diff --git a/README.md b/README.md
index d4bb96fa..0a100065 100644
--- a/README.md
+++ b/README.md
@@ -118,3 +118,11 @@ TUF has four major classes of users: clients, for whom TUF is largely transparen
 * [Low-level Integration](tuf/client/README.md)
 
 * [High-level Integration](tuf/interposition/README.md)
+
+## Acknowledgements
+
+This material is based upon work supported by the National Science Foundation
+under Grant No. CNS-1345049 and CNS-0959138. Any opinions, findings, and
+conclusions or recommendations expressed in this material are those of the
+author(s) and do not necessarily reflect the views of the National Science
+Foundation.
diff --git a/dev-requirements.txt b/dev-requirements.txt
index 2f1d0d60..4310cb16 100644
--- a/dev-requirements.txt
+++ b/dev-requirements.txt
@@ -17,4 +17,7 @@
 # http://nvie.com/posts/pin-your-packages/
 pycrypto==2.6.1
 pynacl==0.2.3
+
+# Testing requirements.  The rest of the testing dependencies available in
+# 'tox.ini'
 tox
diff --git a/setup.py b/setup.py
index 17867ca0..78a994d1 100755
--- a/setup.py
+++ b/setup.py
@@ -96,6 +96,10 @@
     'Programming Language :: Python :: 2',
     'Programming Language :: Python :: 2.6',
     'Programming Language :: Python :: 2.7',
+    'Programming Language :: Python :: 3',
+    'Programming Language :: Python :: 3.2',
+    'Programming Language :: Python :: 3.3',
+    'Programming Language :: Python :: 3.4',
     'Programming Language :: Python :: Implementation :: CPython',
     'Topic :: Security',
     'Topic :: Software Development'
diff --git a/tests/repository_data/generate.py b/tests/repository_data/generate.py
index 15e5a661..2eba6da0 100755
--- a/tests/repository_data/generate.py
+++ b/tests/repository_data/generate.py
@@ -29,25 +29,41 @@
 from tuf.repository_tool import *
 import tuf.util
 
+import optparse
+
+parser = optparse.OptionParser()
+parser.add_option("-k","--keys", action='store_true',  dest="should_generate_keys",
+    help="Generate a new set of keys", default=False)
+parser.add_option("-d","--dry-run", action='store_true', dest="dry_run",
+    help="Do not write the files, just run", default=False)
+(options, args) = parser.parse_args()
+
+
 repository = create_new_repository('repository')
 
-# Generate and save the top-level role keys, including the delegated roles.
-# The unit tests should only have to import the keys they need from these
-# pre-generated key files.
 root_key_file = 'keystore/root_key'
 targets_key_file = 'keystore/targets_key' 
 snapshot_key_file = 'keystore/snapshot_key'
 timestamp_key_file = 'keystore/timestamp_key'
 delegation_key_file = 'keystore/delegation_key'
 
-# Generate public and private key files for the top-level roles, and two
-# delegated roles (these number of keys should be sufficient for most of the
-# unit tests).  Unit tests may generate additional keys, if needed.
-generate_and_write_rsa_keypair(root_key_file, bits=2048, password='password')
-generate_and_write_rsa_keypair(targets_key_file, bits=2048, password='password')
-generate_and_write_rsa_keypair(snapshot_key_file, bits=2048, password='password')
-generate_and_write_rsa_keypair(timestamp_key_file, bits=2048, password='password')
-generate_and_write_rsa_keypair(delegation_key_file, bits=2048, password='password')
+
+if options.should_generate_keys and not options.dry_run:
+  # Generate and save the top-level role keys, including the delegated roles.
+  # The unit tests should only have to import the keys they need from these
+  # pre-generated key files.
+  # Generate public and private key files for the top-level roles, and two
+  # delegated roles (these number of keys should be sufficient for most of the
+  # unit tests).  Unit tests may generate additional keys, if needed.
+  generate_and_write_rsa_keypair(root_key_file, bits=2048, password='password')
+  generate_and_write_rsa_keypair(targets_key_file, bits=2048,
+      password='password')
+  generate_and_write_rsa_keypair(snapshot_key_file, bits=2048,
+      password='password')
+  generate_and_write_rsa_keypair(timestamp_key_file, bits=2048,
+      password='password')
+  generate_and_write_rsa_keypair(delegation_key_file, bits=2048,
+      password='password')
 
 # Import the public keys.  These keys are needed so that metadata roles are
 # assigned verification keys, which clients use to verify the signatures created
@@ -88,14 +104,15 @@
 target3_filepath = 'repository/targets/file3.txt'
 tuf.util.ensure_parent_dir(target2_filepath)
 
-with open(target1_filepath, 'wt') as file_object:
-  file_object.write('This is an example target file.')
+if not options.dry_run:
+  with open(target1_filepath, 'wt') as file_object:
+    file_object.write('This is an example target file.')
 
-with open(target2_filepath, 'wt') as file_object:
-  file_object.write('This is an another example target file.')
+  with open(target2_filepath, 'wt') as file_object:
+    file_object.write('This is an another example target file.')
 
-with open(target3_filepath, 'wt') as file_object:
-  file_object.write('This is role1\'s target file.')
+  with open(target3_filepath, 'wt') as file_object:
+    file_object.write('This is role1\'s target file.')
 
 # Add target files to the top-level 'targets.json' role.  These target files
 # should already exist.
@@ -119,15 +136,18 @@
 repository.targets.compressions = ['gz']
 
 # Create the actual metadata files, which are saved to 'metadata.staged'. 
-repository.write()
+if not options.dry_run:
+  repository.write()
 
 # Move the staged.metadata to 'metadata' and create the client folder.  The
 # client folder, which includes the required directory structure and metadata
 # files for clients to successfully load an 'tuf.client.updater.py' object.
 staged_metadata_directory = 'repository/metadata.staged'
 metadata_directory = 'repository/metadata'
-shutil.copytree(staged_metadata_directory, metadata_directory)
+if not options.dry_run:
+  shutil.copytree(staged_metadata_directory, metadata_directory)
 
 # Create the client files (required directory structure and minimal metadata)
 # required by the 'tuf.interposition' and 'tuf.client.updater.py' updaters.
-create_tuf_client_directory('repository', 'client')
+if not options.dry_run:
+  create_tuf_client_directory('repository', 'client')
diff --git a/tests/test_arbitrary_package_attack.py b/tests/test_arbitrary_package_attack.py
index 0d9a9221..83061e97 100755
--- a/tests/test_arbitrary_package_attack.py
+++ b/tests/test_arbitrary_package_attack.py
@@ -89,7 +89,7 @@ def setUpClass(cls):
 
     # NOTE: Following error is raised if a delay is not applied:
     # <urlopen error [Errno 111] Connection refused>
-    time.sleep(.2)
+    time.sleep(1)
 
 
 
diff --git a/tests/test_download.py b/tests/test_download.py
index f3fbaa1f..f8aca54e 100755
--- a/tests/test_download.py
+++ b/tests/test_download.py
@@ -170,13 +170,28 @@ def test_download_url_to_tempfileobj_and_urls(self):
 
     self.assertRaises(six.moves.urllib.error.HTTPError,
                       download_file,
-                      'http://localhost:'+str(self.PORT)+'/'+self.random_string(), 
+                      'http://localhost:' + str(self.PORT) + '/' + self.random_string(), 
                       self.target_data_length)
 
     self.assertRaises(six.moves.urllib.error.URLError,
                       download_file,
-                      'http://localhost:'+str(self.PORT+1)+'/'+self.random_string(), 
+                      'http://localhost:' + str(self.PORT+1) + '/' + self.random_string(), 
                       self.target_data_length)
+ 
+
+
+  def test__get_opener(self):
+    # Test normal case.
+    # A simple https server should be used to test the rest of the optional
+    # ssl-related functions of 'tuf.download.py'.
+    fake_cacert = self.make_temp_data_file()
+    
+    with open(fake_cacert, 'wt') as file_object:
+      file_object.write('fake cacert')
+    
+    tuf.conf.ssl_certificates = fake_cacert
+    tuf.download._get_opener('https')
+    
 
 
 # Run unit test.
diff --git a/tests/test_endless_data_attack.py b/tests/test_endless_data_attack.py
index 00382f25..b81a23f9 100755
--- a/tests/test_endless_data_attack.py
+++ b/tests/test_endless_data_attack.py
@@ -92,7 +92,7 @@ def setUpClass(cls):
 
     # NOTE: Following error is raised if a delay is not applied:
     # <urlopen error [Errno 111] Connection refused>
-    time.sleep(.5)
+    time.sleep(.8)
 
 
 
diff --git a/tests/test_indefinite_freeze_attack.py b/tests/test_indefinite_freeze_attack.py
index 436198d4..8d24a687 100755
--- a/tests/test_indefinite_freeze_attack.py
+++ b/tests/test_indefinite_freeze_attack.py
@@ -92,7 +92,7 @@ def setUpClass(cls):
 
     # NOTE: Following error is raised if a delay is not applied:
     # <urlopen error [Errno 111] Connection refused>
-    time.sleep(.2)
+    time.sleep(.8)
 
 
 
diff --git a/tests/test_mix_and_match_attack.py b/tests/test_mix_and_match_attack.py
index 69ed0594..e44f7927 100755
--- a/tests/test_mix_and_match_attack.py
+++ b/tests/test_mix_and_match_attack.py
@@ -96,7 +96,7 @@ def setUpClass(cls):
 
     # NOTE: Following error is raised if a delay is not applied:
     # <urlopen error [Errno 111] Connection refused>
-    time.sleep(.2)
+    time.sleep(.8)
 
 
 
diff --git a/tests/test_replay_attack.py b/tests/test_replay_attack.py
index dad8269d..aba4b227 100755
--- a/tests/test_replay_attack.py
+++ b/tests/test_replay_attack.py
@@ -97,7 +97,7 @@ def setUpClass(cls):
 
     # NOTE: Following error is raised if a delay is not applied:
     # <urlopen error [Errno 111] Connection refused>
-    time.sleep(.2)
+    time.sleep(.8)
 
 
 
diff --git a/tests/test_repository_lib.py b/tests/test_repository_lib.py
index 017e63ae..9885e476 100755
--- a/tests/test_repository_lib.py
+++ b/tests/test_repository_lib.py
@@ -30,6 +30,7 @@
 import datetime
 import logging
 import tempfile
+import json
 import shutil
 import sys
 
@@ -262,6 +263,20 @@ def test_import_ed25519_publickey_from_file(self):
     
     self.assertRaises(tuf.Error, repo_lib.import_ed25519_publickey_from_file,
                       invalid_keyfile)
+ 
+    # Invalid public key imported (contains unexpected keytype.)
+    keytype = imported_ed25519_key['keytype'] 
+    keyval = imported_ed25519_key['keyval']
+    ed25519key_metadata_format = \
+      tuf.keys.format_keyval_to_metadata(keytype, keyval, private=False)
+    
+    ed25519key_metadata_format['keytype'] = 'invalid_keytype'
+    with open(ed25519_keypath + '.pub', 'wb') as file_object:
+      file_object.write(json.dumps(ed25519key_metadata_format).encode('utf-8'))
+    
+    self.assertRaises(tuf.FormatError,
+                      repo_lib.import_ed25519_publickey_from_file,
+                      ed25519_keypath + '.pub')
 
 
 
@@ -296,6 +311,32 @@ def test_import_ed25519_privatekey_from_file(self):
     
     self.assertRaises(tuf.Error, repo_lib.import_ed25519_privatekey_from_file,
                       invalid_keyfile, 'pw')
+    
+    # Invalid private key imported (contains unexpected keytype.)
+    imported_ed25519_key['keytype'] = 'invalid_keytype'
+
+    # Use 'pycrypto_keys.py' to bypass the key format validation performed by
+    # 'keys.py'.
+    salt, iterations, derived_key = \
+      tuf.pycrypto_keys._generate_derived_key('pw')
+ 
+    # Store the derived key info in a dictionary, the object expected
+    # by the non-public _encrypt() routine.
+    derived_key_information = {'salt': salt, 'iterations': iterations,
+                               'derived_key': derived_key}
+
+    # Convert the key object to json string format and encrypt it with the
+    # derived key.
+    encrypted_key = \
+      tuf.pycrypto_keys._encrypt(json.dumps(imported_ed25519_key),
+                                 derived_key_information)  
+    
+    with open(ed25519_keypath, 'wb') as file_object:
+      file_object.write(encrypted_key.encode('utf-8'))
+
+    self.assertRaises(tuf.FormatError,
+                      repo_lib.import_ed25519_privatekey_from_file,
+                      ed25519_keypath, 'pw')
 
 
 
@@ -677,6 +718,12 @@ def test_create_tuf_client_directory(self):
                       repository_directory, client_directory)
 
 
+  def test__check_directory(self):
+    # Test for non-existent directory.
+    self.assertRaises(tuf.Error, repo_lib._check_directory, 'non-existent')
+
+
+
 # Run the test cases.
 if __name__ == '__main__':
   unittest.main()
diff --git a/tests/test_updater.py b/tests/test_updater.py
index 663e2cb0..515d74b5 100755
--- a/tests/test_updater.py
+++ b/tests/test_updater.py
@@ -1103,6 +1103,25 @@ def test_8_remove_obsolete_targets(self):
     #  in 'destination_directory' remains the same.
     self.repository_updater.remove_obsolete_targets(destination_directory)
     self.assertTrue(os.listdir(destination_directory), 1)    
+ 
+
+
+
+
+  def test_9__get_target_hash(self):
+    # Test normal case.
+    # Test target filepaths with ascii and non-ascii characters.
+    expected_target_hashes = {
+      '/file1.txt': 'e3a3d89eb3b70ce3fbce6017d7b8c12d4abd5635427a0e8a238f53157df85b3d',
+      '/Jalape\xc3\xb1o': '78bfd5c314680545eb48ecad508aceb861f8d6e680f4fe1b791da45c298cda88' 
+    }
+    for filepath, target_hash in six.iteritems(expected_target_hashes):
+      self.assertTrue(tuf.formats.RELPATH_SCHEMA.matches(filepath))
+      self.assertTrue(tuf.formats.HASH_SCHEMA.matches(target_hash))
+      self.assertEqual(self.repository_updater._get_target_hash(filepath), target_hash)
+   
+    # Test for improperly formatted argument.
+    self.assertRaises(tuf.FormatError, tuf.util.get_target_hash, 8)
 
 
 
diff --git a/tox.ini b/tox.ini
index 36329a74..0c586e04 100644
--- a/tox.ini
+++ b/tox.ini
@@ -19,6 +19,7 @@ deps =
     pynacl
     pycrypto
 
+
 [testenv:py26]
 deps =
     {[testenv]deps}
diff --git a/tuf/client/updater.py b/tuf/client/updater.py
index e3ff4640..5f7d4802 100755
--- a/tuf/client/updater.py
+++ b/tuf/client/updater.py
@@ -2448,16 +2448,17 @@ def _visit_child_role(self, child_role, target_filepath):
       # 'role_name' should have been validated when it was downloaded.
       # The 'paths' or 'path_hash_prefixes' fields should not be missing,
       # so we raise a format error here in case they are both missing.
-      raise tuf.FormatError(repr(child_role_name)+' has neither ' \
+      raise tuf.FormatError(repr(child_role_name) + ' has neither ' \
                                 '"paths" nor "path_hash_prefixes".')
 
     if child_role_is_relevant:
-      logger.debug('Child role '+repr(child_role_name)+' has target '+
+      logger.debug('Child role ' + repr(child_role_name) + ' has target ' + \
                    repr(target_filepath))
       return child_role_name
+    
     else:
-      logger.debug('Child role '+repr(child_role_name)+
-                   ' does not have target '+repr(target_filepath))
+      logger.debug('Child role ' + repr(child_role_name) + \
+                   ' does not have target ' + repr(target_filepath))
       return None
 
 
@@ -2495,20 +2496,11 @@ def _get_target_hash(self, target_filepath, hash_function='sha256'):
     """
 
     # Calculate the hash of the filepath to determine which bin to find the 
-    # target.  The client currently assumes the repository uses
-    # 'hash_function' to generate hashes.
-
+    # target.  The client currently assumes the repository (i.e., repository
+    # tool) uses 'hash_function' to generate hashes and UTF-8.
     digest_object = tuf.hash.digest(hash_function)
-
-    try:
-      digest_object.update(target_filepath)
-    except UnicodeEncodeError:
-      # Sometimes, there are Unicode characters in target paths. We assume a
-      # UTF-8 encoding and try to hash that.
-      digest_object = tuf.hash.digest(hash_function)
-      encoded_target_filepath = target_filepath.encode('utf-8')
-      digest_object.update(encoded_target_filepath)
-
+    encoded_target_filepath = target_filepath.encode('utf-8')
+    digest_object.update(encoded_target_filepath)
     target_filepath_hash = digest_object.hexdigest() 
 
     return target_filepath_hash
@@ -2554,7 +2546,7 @@ def remove_obsolete_targets(self, destination_directory):
           for target in self.metadata['previous'][role]['targets']:
             if target not in self.metadata['current'][role]['targets']:
               # 'target' is only in 'previous', so remove it.
-              logger.warning('Removing obsolete file: '+repr(target)+'.')
+              logger.warning('Removing obsolete file: ' + repr(target) + '.')
               # Remove the file if it hasn't been removed already.
               destination = os.path.join(destination_directory, target) 
               try:
@@ -2563,7 +2555,7 @@ def remove_obsolete_targets(self, destination_directory):
               except OSError as e:
                 # If 'filename' already removed, just log it.
                 if e.errno == errno.ENOENT:
-                  logger.info('File '+repr(destination)+' was already removed.')
+                  logger.info('File ' + repr(destination) + ' was already removed.')
                 
                 else:
                   logger.error(str(e))
@@ -2722,6 +2714,6 @@ def download_target(self, target, destination_directory):
           raise
     
     else:
-      logger.warning(str(target_dirpath)+' does not exist.')
+      logger.warning(repr(target_dirpath) + ' does not exist.')
 
     target_file_object.move(destination)
diff --git a/tuf/download.py b/tuf/download.py
index 08e0fc84..0eab6606 100755
--- a/tuf/download.py
+++ b/tuf/download.py
@@ -461,8 +461,9 @@ def _get_content_length(connection):
     assert reported_length > -1
   
   except:
-    logger.exception('Could not get content length about '+str(connection)+
-                     ' from server!')
+    message = \
+      'Could not get content length about ' + str(connection) + ' from server.'
+    logger.exception(message)
     reported_length = None
   
   finally:
diff --git a/tuf/repository_lib.py b/tuf/repository_lib.py
index d4d8d69b..b32d251e 100755
--- a/tuf/repository_lib.py
+++ b/tuf/repository_lib.py
@@ -231,11 +231,14 @@ def _get_password(prompt='Password: ', confirm=False):
     # getpass() prompts the user for a password without echoing
     # the user input.
     password = getpass.getpass(prompt, sys.stderr)
+    
     if not confirm:
       return password
     password2 = getpass.getpass('Confirm: ', sys.stderr)
+    
     if password == password2:
       return password
+    
     else:
       print('Mismatch; try again.')
 
@@ -246,10 +249,14 @@ def _get_password(prompt='Password: ', confirm=False):
 def _metadata_is_partially_loaded(rolename, signable, roleinfo):
   """
   Non-public function that determines whether 'rolename' is loaded with
-  at least 1 good signature, but an insufficient threshold (which means
-  'rolename' was written to disk with repository.write_partial().  If 'rolename'
-  is found to be partially loaded, mark it as partially loaded in its
-  'tuf.roledb' roleinfo.  This function exists to assist in deciding whether
+  at least zero good signatures, but an insufficient threshold (which means
+  'rolename' was written to disk with repository.write_partial()).  A repository
+  maintainer may write partial metadata without including a valid signature.
+  Howerver, the final repository.write() must include a threshold number of
+  signatures.
+  
+  If 'rolename' is found to be partially loaded, mark it as partially loaded in
+  its 'tuf.roledb' roleinfo.  This function exists to assist in deciding whether
   a role's version number should be incremented when write() or write_parital()
   is called.  Return True if 'rolename' was partially loaded, False otherwise. 
   """
@@ -259,7 +266,7 @@ def _metadata_is_partially_loaded(rolename, signable, roleinfo):
   status = tuf.sig.get_signature_status(signable, rolename)
   
   if len(status['good_sigs']) < status['threshold'] and \
-                                                  len(status['good_sigs']) >= 1:
+                                                  len(status['good_sigs']) >= 0:
     return True
   
   else:
@@ -299,7 +306,7 @@ def _check_directory(directory):
 
   # Check if the directory exists.
   if not os.path.isdir(directory):
-    raise tuf.Error(repr(directory)+' directory does not exist.')
+    raise tuf.Error(repr(directory) + ' directory does not exist.')
 
   directory = os.path.abspath(directory)
   
@@ -326,14 +333,14 @@ def _check_role_keys(rolename):
  
   # Raise an exception for an invalid threshold of public keys.
   if total_keyids < threshold: 
-    message = repr(rolename)+' role contains '+repr(total_keyids)+' / '+ \
-      repr(threshold)+' public keys.'
+    message = repr(rolename) + ' role contains ' + \
+      repr(total_keyids) + ' / ' + repr(threshold) + ' public keys.'
     raise tuf.InsufficientKeysError(message)
 
   # Raise an exception for an invalid threshold of signing keys.
   if total_signatures == 0 and total_signing_keys < threshold: 
-    message = repr(rolename)+' role contains '+repr(total_signing_keys)+' / '+ \
-      repr(threshold)+' signing keys.'
+    message = repr(rolename) + ' role contains ' + \
+      repr(total_signing_keys) + ' / ' + repr(threshold) + ' signing keys.'
     raise tuf.InsufficientKeysError(message)
 
 
@@ -494,7 +501,7 @@ def _strip_consistent_snapshot_digest(metadata_filename, consistent_snapshot):
     embeded_digest = basename[:basename.find('.')]
     
     # Ensure the digest, including the period, is stripped.
-    basename = basename[basename.find('.')+1:]
+    basename = basename[basename.find('.') + 1:]
     
     metadata_filename = os.path.join(dirname, basename)
   
@@ -754,7 +761,7 @@ def generate_and_write_rsa_keypair(filepath, bits=DEFAULT_RSA_KEY_BITS,
   tuf.formats.RSAKEYBITS_SCHEMA.check_match(bits)
 
   # If the caller does not provide a password argument, prompt for one.
-  if password is None:
+  if password is None: # pragma: no cover
     message = 'Enter a password for the RSA key file: '
     password = _get_password(message, confirm=True)
 
@@ -779,7 +786,7 @@ def generate_and_write_rsa_keypair(filepath, bits=DEFAULT_RSA_KEY_BITS,
   file_object.write(public.encode('utf-8'))
   
   # The temporary file is closed after the final move.
-  file_object.move(filepath+'.pub')
+  file_object.move(filepath + '.pub')
 
   # Write the private key in encrypted PEM format to '<filepath>'.
   # Unlike the public key file, the private key does not have a file
@@ -834,7 +841,7 @@ def import_rsa_privatekey_from_file(filepath, password=None):
   # If the caller does not provide a password argument, prompt for one.
   # Password confirmation disabled here, which should ideally happen only
   # when creating encrypted key files (i.e., improve usability).
-  if password is None:
+  if password is None: # pragma: no cover
     message = 'Enter a password for the encrypted RSA file: '
     password = _get_password(message, confirm=False)
 
@@ -955,7 +962,7 @@ def generate_and_write_ed25519_keypair(filepath, password=None):
   tuf.formats.PATH_SCHEMA.check_match(filepath)
 
   # If the caller does not provide a password argument, prompt for one.
-  if password is None:
+  if password is None: # pragma: no cover
     message = 'Enter a password for the ED25519 key: '
     password = _get_password(message, confirm=True)
 
@@ -986,7 +993,7 @@ def generate_and_write_ed25519_keypair(filepath, password=None):
   file_object.write(json.dumps(ed25519key_metadata_format).encode('utf-8'))
   
   # The temporary file is closed after the final move.
-  file_object.move(filepath+'.pub')
+  file_object.move(filepath + '.pub')
 
   # Write the encrypted key string, conformant to
   # 'tuf.formats.ENCRYPTEDKEY_SCHEMA', to '<filepath>'.
@@ -1034,9 +1041,11 @@ def import_ed25519_publickey_from_file(filepath):
   ed25519_key_metadata = tuf.util.load_json_file(filepath)
   ed25519_key = tuf.keys.format_metadata_to_key(ed25519_key_metadata)
   
-  # Raise an exception if an unexpected key type is imported. 
-  if ed25519_key['keytype'] != 'ed25519':
-    message = 'Invalid key type loaded: '+repr(ed25519_key['keytype'])
+  # Raise an exception if an unexpected key type is imported.
+  # Redundant validation of 'keytype'.  'tuf.keys.format_metadata_to_key()'
+  # should have fully validated 'ed25519_key_metadata'.
+  if ed25519_key['keytype'] != 'ed25519': # pragma: no cover
+    message = 'Invalid key type loaded: ' + repr(ed25519_key['keytype'])
     raise tuf.FormatError(message)
 
   return ed25519_key
@@ -1093,7 +1102,7 @@ def import_ed25519_privatekey_from_file(filepath, password=None):
   # If the caller does not provide a password argument, prompt for one.
   # Password confirmation disabled here, which should ideally happen only
   # when creating encrypted key files (i.e., improve usability).
-  if password is None:
+  if password is None: # pragma: no cover
     message = 'Enter a password for the encrypted ED25519 key: '
     password = _get_password(message, confirm=False)
 
@@ -1115,7 +1124,7 @@ def import_ed25519_privatekey_from_file(filepath, password=None):
 
   # Raise an exception if an unexpected key type is imported. 
   if key_object['keytype'] != 'ed25519':
-    message = 'Invalid key type loaded: '+repr(key_object['keytype'])
+    message = 'Invalid key type loaded: ' + repr(key_object['keytype'])
     raise tuf.FormatError(message)
 
   return key_object
@@ -1223,7 +1232,7 @@ def get_metadata_fileinfo(filename):
   tuf.formats.PATH_SCHEMA.check_match(filename)
 
   if not os.path.isfile(filename):
-    message = repr(filename)+' is not a file.'
+    message = repr(filename) + ' is not a file.'
     raise tuf.Error(message)
   
   # Note: 'filehashes' is a dictionary of the form
@@ -1330,7 +1339,7 @@ def generate_root_metadata(version, expiration_date, consistent_snapshot):
     
     # If a top-level role is missing from 'tuf.roledb.py', raise an exception.
     if not tuf.roledb.role_exists(rolename):
-      raise tuf.Error(repr(rolename)+' not in "tuf.roledb".')
+      raise tuf.Error(repr(rolename) + ' not in "tuf.roledb".')
    
     # Keep track of the keys loaded to avoid duplicates.
     keyids = []
@@ -1469,7 +1478,7 @@ def generate_targets_metadata(targets_directory, target_files, version,
     # Ensure all target files listed in 'target_files' exist.  If just one of
     # these files does not exist, raise an exception.
     if not os.path.exists(target_path):
-      message = repr(target_path)+' cannot be read.  Unable to generate '+ \
+      message = repr(target_path) + ' cannot be read.  Unable to generate '+ \
         'targets metadata.'
       raise tuf.Error(message)
     
@@ -1685,10 +1694,10 @@ def generate_timestamp_metadata(snapshot_filename, version,
       compressed_fileinfo = get_metadata_fileinfo(compressed_filename)
     
     except:
-      logger.warning('Cannot get fileinfo about '+repr(compressed_filename))
+      logger.warning('Cannot get fileinfo about ' + repr(compressed_filename))
     
     else:
-      logger.info('Including fileinfo about '+repr(compressed_filename))
+      logger.info('Including fileinfo about ' + repr(compressed_filename))
       fileinfo[SNAPSHOT_FILENAME + '.' + file_extension] = compressed_fileinfo
 
   # Generate the timestamp metadata object.
@@ -1754,7 +1763,7 @@ def sign_metadata(metadata_object, keyids, filename):
     
     # Load the signing key.
     key = tuf.keydb.get_key(keyid)
-    logger.info('Signing '+repr(filename)+' with '+key['keyid'])
+    logger.info('Signing ' + repr(filename) + ' with ' + key['keyid'])
 
     # Create a new signature list.  If 'keyid' is encountered, do not add it
     # to the new list.
@@ -1772,7 +1781,7 @@ def sign_metadata(metadata_object, keyids, filename):
         signable['signatures'].append(signature)
       
       else:
-        logger.warning('Private key unset.  Skipping: '+repr(keyid))
+        logger.warning('Private key unset.  Skipping: ' + repr(keyid))
     
     else:
       raise tuf.Error('The keydb contains a key with an invalid key type.')
@@ -2095,8 +2104,8 @@ def _log_status(rolename, signable):
   
   status = tuf.sig.get_signature_status(signable, rolename)
 
-  message = repr(rolename)+' role contains '+ repr(len(status['good_sigs']))+\
-    ' / '+repr(status['threshold'])+' signatures.'
+  message = repr(rolename) + ' role contains ' + repr(len(status['good_sigs']))+\
+    ' / ' + repr(status['threshold']) + ' signatures.'
   logger.info(message)
 
 
@@ -2173,6 +2182,7 @@ def create_tuf_client_directory(repository_directory, client_directory):
       message = 'Cannot create a fresh client metadata directory: '+ \
         repr(client_metadata_directory)+'.  Already exists.'
       raise tuf.RepositoryError(message)
+    
     else:
       raise
 
diff --git a/tuf/repository_tool.py b/tuf/repository_tool.py
index c6466cb1..598e20fb 100755
--- a/tuf/repository_tool.py
+++ b/tuf/repository_tool.py
@@ -2675,7 +2675,7 @@ def load_repository(repository_directory):
         roleinfo['paths'] = list(metadata_object['targets'].keys())
         roleinfo['delegations'] = metadata_object['delegations']
 
-        if os.path.exists(metadata_path+'.gz'):
+        if os.path.exists(metadata_path + '.gz'):
           roleinfo['compressions'].append('gz')
        
         # The roleinfo of 'metadata_name' should have been initialized with