Running captainhook in child directory causes errors

[Andrew Pinkham]

When I install captainhook via pip, running captainhook run in a child directory causes the following error.

$ # in a child directory (child of the project root)
$ pwd
project/src
$ captainhook run
Traceback (most recent call last):
  File "project/.git/hooks/pre-commit", line 127, in <module>
    exit_code = main(commit_only=not args.all)
  File "project/.git/hooks/pre-commit", line 107, in main
    errors = mod.run(files, TEMP_FOLDER)
  File "project/.git/hooks/checkers/flake8_checker.py", line 39, in run
    py_files = filter_python_files(files)
  File "project/.git/hooks/checkers/utils.py", line 106, in filter_python_files
    elif 'python' in open(f, 'r').readline():
FileNotFoundError: [Errno 2] No such file or directory: '.gitignore'

This is likely because of the command "git ls-tree --name-only --full-tree -r HEAD" in captainhook/checkers/utils.py.

In the development version of the code (which appears to be different?) the command fails silently.

$ git ci
===============================================================================
Checking isort
===============================================================================
--- src/test.py:before  2015-08-15 09:22:34
+++ src/test.py:after   2015-08-15 09:22:35.491702
@@ -1,5 +1,5 @@
+import os
+
 import django

-import os
-
 boo()

===============================================================================
Rejecting commit
===============================================================================
$ captainhook run
$ # no output!