Fix test since pip 10 changed output

testing/resources/not_installable_repo/.pre-commit-hooks.yaml

@@ -1,6 +0,0 @@
--   id: foo
-    name: Foo
-    entry: foo
-    language: python
-    language_version: python2.7
-    files: \.py$

testing/resources/not_installable_repo/setup.py

@@ -1,17 +0,0 @@
-# -*- coding: utf-8 -*-
-from __future__ import print_function
-from __future__ import unicode_literals
-
-import sys
-
-
-def main():
-    # Intentionally write mixed encoding to the output.  This should not crash
-    # pre-commit and should write bytes to the output.
-    sys.stderr.write('☃'.encode('UTF-8') + '²'.encode('latin1') + b'\n')
-    # Return 1 to indicate failures
-    return 1
-
-
-if __name__ == '__main__':
-    exit(main())