test_pullWithUnnormalizedPath fails in python3 tests.

For example here
https://circleci.com/gh/box/wavectl/309

The test_pullWithUnnormalizedPath test actually failed. Gave this output:
```
[test_pullWithUnnormalizedPath.py] ERROR:git.config:Exception during destruction of GitConfigParser
[test_pullWithUnnormalizedPath.py] Traceback (most recent call last):
[test_pullWithUnnormalizedPath.py] File "/home/circleci/project/venv/lib64/python3.6/os.py", line 666, in __getitem__
[test_pullWithUnnormalizedPath.py] value = self._data[self.encodekey(key)]
[test_pullWithUnnormalizedPath.py] KeyError: b'COLUMNS'
[test_pullWithUnnormalizedPath.py]
[test_pullWithUnnormalizedPath.py] During handling of the above exception, another exception occurred:
[test_pullWithUnnormalizedPath.py]
[test_pullWithUnnormalizedPath.py] Traceback (most recent call last):
[test_pullWithUnnormalizedPath.py] File "/home/circleci/project/venv/lib/python3.6/site-packages/git/config.py", line 259, in release
[test_pullWithUnnormalizedPath.py] self.write()
[test_pullWithUnnormalizedPath.py] File "/home/circleci/project/venv/lib/python3.6/site-packages/git/config.py", line 79, in assure_data_present
[test_pullWithUnnormalizedPath.py] return func(self, *args, **kwargs)
[test_pullWithUnnormalizedPath.py] File "/home/circleci/project/venv/lib/python3.6/site-packages/git/config.py", line 488, in write
[test_pullWithUnnormalizedPath.py] with open(self._file_or_files, "wb") as fp:
[test_pullWithUnnormalizedPath.py] FileNotFoundError: [Errno 2] No such file or directory: '/tmp/tmpxykt9gv0/.git/config'
[test_pullWithUnnormalizedPath.py] .
[test_pullWithUnnormalizedPath.py] ----------------------------------------------------------------------
[test_pullWithUnnormalizedPath.py] Ran 1 test in 3.850s
[test_pullWithUnnormalizedPath.py]
[test_pullWithUnnormalizedPath.py] OK
```

1) Why is this test failing in python3 only. It passes in python2
2) Even though there was an exeption, why did the python unittest pass and print this :`[test_pullWithUnnormalizedPath.py] OK` ?