versiontools tests fail with Python 3.5

[Benjamin Drung]

The test cases of versiontools 1.9.1 fail:

======================================================================
FAIL: test_not_found (versiontools.tests.HandleVersionTests)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/versiontools-1.9.1/versiontools/__init__.py", line 241, in from_expression
    version = getattr(obj, identifier)
AttributeError: module 'versiontools' has no attribute '__nonexisting__'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/versiontools-1.9.1/versiontools/setuptools_hooks.py", line 64, in version
    version = Version.from_expression(value)
ValueError: Unable to access '__nonexisting__' in 'versiontools': module 'versiontools' has no attribute '__nonexisting__'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/versiontools-1.9.1/versiontools/tests.py", line 147, in test_not_found
    handle_version(self.dist, None, version)
distutils.errors.DistutilsSetupError: Unable to access '__nonexisting__' in 'versiontools': module 'versiontools' has no attribute '__nonexisting__'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/versiontools-1.9.1/versiontools/tests.py", line 151, in test_not_found
    self.assertEqual(str(e), "Unable to access '__nonexisting__' in "
AssertionError: "Unab[44 chars]ols': module 'versiontools' has no attribute '__nonexisting__'" != "Unab[44 chars]ols': 'module' object has no attribute '__nonexisting__'"
- Unable to access '__nonexisting__' in 'versiontools': module 'versiontools' has no attribute '__nonexisting__'
? - ^ ^^^^^ -----
+ Unable to access '__nonexisting__' in 'versiontools': 'module' object has no attribute '__nonexisting__'
? + ^^^^ ^

[Benjamin Drung (bdrung)]

A patch is attached that fixes the not_found test failure for Python 3.5.