this unit test breaks with:
```
EF.......EEE.F.E.EE.
======================================================================
ERROR: test_1__load_metadata_from_file (__main__.TestUpdater)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "test_updater.py", line 372, in test_1__load_metadata_from_file
    self.Repository.refresh()
  File "/home/santiago/Documents/p2014/TUF/tuf-tests/tuf/tuf/client/updater.py", line 618, in refresh
    self._update_metadata('root', DEFAULT_ROOT_FILEINFO)
  File "/home/santiago/Documents/p2014/TUF/tuf-tests/tuf/tuf/client/updater.py", line 1278, in _update_metadata
    compression, compressed_fileinfo)
  File "/home/santiago/Documents/p2014/TUF/tuf-tests/tuf/tuf/client/updater.py", line 998, in _unsafely_get_metadata_file
    download_safely=False)
  File "/home/santiago/Documents/p2014/TUF/tuf-tests/tuf/tuf/client/updater.py", line 1183, in _get_file
    raise tuf.NoWorkingMirrorError(file_mirror_errors)
NoWorkingMirrorError: No working mirror was found:
  mirror2.com: HTTP Error 403: (Forbidden)
  mirror1.com: HTTP Error 403: (Forbidden)
  mirror3.com: No JSON object could be decoded

======================================================================
ERROR: test_3__update_metadata (__main__.TestUpdater)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "test_updater.py", line 661, in test_3__update_metadata
    compressed_fileinfo=compressed_fileinfo)
  File "/home/santiago/Documents/p2014/TUF/tuf-tests/tuf/tuf/client/updater.py", line 1296, in _update_metadata
    compression, compressed_fileinfo)
  File "/home/santiago/Documents/p2014/TUF/tuf-tests/tuf/tuf/client/updater.py", line 1078, in _safely_get_metadata_file
    download_safely=True)
  File "/home/santiago/Documents/p2014/TUF/tuf-tests/tuf/tuf/client/updater.py", line 1183, in _get_file
    raise tuf.NoWorkingMirrorError(file_mirror_errors)
NoWorkingMirrorError: No working mirror was found:
  mirror1.com: Observed length (3123) <= expected length (1792)
  mirror2.com: Observed length (3123) <= expected length (1792)
  mirror3.com: Observed length (3123) <= expected length (1792)

======================================================================
ERROR: test_3__update_metadata_if_changed (__main__.TestUpdater)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "test_updater.py", line 701, in test_3__update_metadata_if_changed
    self.Repository._update_metadata('timestamp', DEFAULT_TIMESTAMP_FILEINFO)
  File "/home/santiago/Documents/p2014/TUF/tuf-tests/tuf/tuf/client/updater.py", line 1272, in _update_metadata
    compression, compressed_fileinfo)
  File "/home/santiago/Documents/p2014/TUF/tuf-tests/tuf/tuf/client/updater.py", line 998, in _unsafely_get_metadata_file
    download_safely=False)
  File "/home/santiago/Documents/p2014/TUF/tuf-tests/tuf/tuf/client/updater.py", line 1183, in _get_file
    raise tuf.NoWorkingMirrorError(file_mirror_errors)
NoWorkingMirrorError: No working mirror was found:
  mirror3.com: 'NoneType' object has no attribute 'items'
  mirror2.com: 'NoneType' object has no attribute 'items'
  mirror1.com: 'NoneType' object has no attribute 'items'

======================================================================
ERROR: test_4__refresh_targets_metadata (__main__.TestUpdater)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "test_updater.py", line 861, in test_4__refresh_targets_metadata
    self._update_top_level_roles()
  File "test_updater.py", line 341, in _update_top_level_roles
    self.Repository._update_metadata('timestamp', DEFAULT_TIMESTAMP_FILEINFO)
  File "/home/santiago/Documents/p2014/TUF/tuf-tests/tuf/tuf/client/updater.py", line 1272, in _update_metadata
    compression, compressed_fileinfo)
  File "/home/santiago/Documents/p2014/TUF/tuf-tests/tuf/tuf/client/updater.py", line 998, in _unsafely_get_metadata_file
    download_safely=False)
  File "/home/santiago/Documents/p2014/TUF/tuf-tests/tuf/tuf/client/updater.py", line 1183, in _get_file
    raise tuf.NoWorkingMirrorError(file_mirror_errors)
NoWorkingMirrorError: No working mirror was found:
  mirror3.com: 'NoneType' object has no attribute 'items'
  mirror2.com: 'NoneType' object has no attribute 'items'
  mirror1.com: 'NoneType' object has no attribute 'items'

======================================================================
ERROR: test_6_download_target (__main__.TestUpdater)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "test_updater.py", line 995, in test_6_download_target
    target_info = self.Repository.target(file_path)
  File "/home/santiago/Documents/p2014/TUF/tuf-tests/tuf/tuf/client/updater.py", line 2188, in target
    raise tuf.UnknownTargetError(message)
UnknownTargetError: /tmpipUSvO.txt not found.

======================================================================
ERROR: test_7_updated_targets (__main__.TestUpdater)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "test_updater.py", line 1048, in test_7_updated_targets
    target_info.append(self.Repository.target(target_path))
  File "/home/santiago/Documents/p2014/TUF/tuf-tests/tuf/tuf/client/updater.py", line 2188, in target
    raise tuf.UnknownTargetError(message)
UnknownTargetError: /tmpipUSvO.txt not found.

======================================================================
ERROR: test_8_remove_obsolete_targets (__main__.TestUpdater)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "test_updater.py", line 1112, in test_8_remove_obsolete_targets
    _target_info = self.Repository.target(target_path)
  File "/home/santiago/Documents/p2014/TUF/tuf-tests/tuf/tuf/client/updater.py", line 2188, in target
    raise tuf.UnknownTargetError(message)
UnknownTargetError: /tmpipUSvO.txt not found.

======================================================================
FAIL: test_1__rebuild_key_and_role_db (__main__.TestUpdater)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "test_updater.py", line 402, in test_1__rebuild_key_and_role_db
    self.assertEqual(tuf.roledb._roledb_dict, self.top_level_role_info)
AssertionError: {u'root': {'signatures': [], 'partial_loaded': False, 'expires': u'2015-02-03 23 [truncated]... != {'snapshot': {'threshold': 1, 'keyids': ['0fbecc2143f397a860985a701fcb1a8447efd8 [truncated]...
Diff is 2006 characters long. Set self.maxDiff to None to see it.

======================================================================
FAIL: test_5_all_targets (__main__.TestUpdater)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "test_updater.py", line 925, in test_5_all_targets
    self.assertTrue(len(all_targets) is 6)
AssertionError: False is not true

----------------------------------------------------------------------
Ran 20 tests in 48.464s

FAILED (failures=2, errors=7)
```
I think there is a semantic/syntax error around somewhere or this test needs further setup.
It crashed on both, MacOS and Linux (tests on windows have not been done yet).