Provide automatic removal of pkg-resources==0.0.0

Should help to deal with that pretty paintuly issue under Ubuntu/Debian
family:
https://bugs.launchpad.net/ubuntu/+source/python-pip/+bug/1635463

Author: nvtkaszpir

pre_commit_hooks/requirements_txt_fixer.py

@@ -69,6 +69,11 @@ def fix_requirements(f):
     else:
         rest = []
 
+    for requirement in requirements:
+        if b'pkg-resources' in requirement.name:
+            if b'0.0.0' in requirement.value:
+                requirements.remove(requirement)
+
     for requirement in sorted(requirements):
         after.extend(requirement.comments)
         after.append(requirement.value)

tests/requirements_txt_fixer_test.py

@@ -28,6 +28,8 @@
             FAIL,
             b'Django\n-e git+ssh://git_url@tag#egg=ocflib\nPyMySQL\n',
         ),
+        (b'bar\npkg-resources==0.0.0\nfoo\n', FAIL, b'bar\nfoo\n'),
+        (b'foo\npkg-resources==0.0.0\nbar\n', FAIL, b'bar\nfoo\n'),
     ),
 )
 def test_integration(input_s, expected_retval, output, tmpdir):