Cannot re-run tests when using freezegun

[andrewmichaelsmith]

I can't use the python package freezegun with my tests and sniffer, I get the issue below.

To reproduce:

Create a file tests.py:

import unittest
from freezegun import freeze_time

class MyTestCase(unittest.TestCase):

        @freeze_time("2015-06-22T17:28:00Z")
        def test_thing(self):
                pass

Then
pip install freezegun

Then

sniffer

Then change a line in tests.py, the second time the tests are run you get this error:

ERROR: Failure: AttributeError ('NoneType' object has no attribute 'timedelta')
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/usr/local/lib/python2.7/dist-packages/nose/loader.py", line 418, in loadTestsFromName
    addr.filename, addr.module)
  File "/usr/local/lib/python2.7/dist-packages/nose/importer.py", line 47, in importFromPath
    return self.importFromDir(dir_path, fqname)
  File "/usr/local/lib/python2.7/dist-packages/nose/importer.py", line 94, in importFromDir
    mod = load_module(part_fqname, fh, filename, desc)
  File "/x/test.py", line 2, in <module>
    from freezegun import freeze_time
  File "/usr/local/lib/python2.7/dist-packages/freezegun/__init__.py", line 18, in <module>
    from .api import freeze_time
  File "/usr/local/lib/python2.7/dist-packages/freezegun/api.py", line 10, in <module>
    from dateutil import parser
  File "/usr/local/lib/python2.7/dist-packages/dateutil/parser.py", line 942, in <module>
    DEFAULTPARSER = parser()
  File "/usr/local/lib/python2.7/dist-packages/dateutil/parser.py", line 341, in __init__
    self.info = info or parserinfo()
  File "/usr/local/lib/python2.7/dist-packages/dateutil/parser.py", line 259, in __init__
    self._year = time.localtime().tm_year
  File "/usr/local/lib/python2.7/dist-packages/freezegun/api.py", line 53, in __call__
    shifted_time = self.time_to_freeze() - datetime.timedelta(seconds=time.timezone)
AttributeError: 'NoneType' object has no attribute 'timedelta'

----------------------------------------------------------------------
Ran 1 test in 0.006s

FAILED (errors=1)
Failed - Back to work!