Try yet another fix of mocking 'git_edit_index.input' in unit tests.
Try yet another fix of mocking 'git_edit_index.input' in unit tests.

According to Travis CI, the solution from commit d383126 does not work on
Python 3.2 - 3.4 and PyPy3, even though with Tox, the tests pass.

s3rvac/git-edit-index