add sys.exit(main()) to file_contents_sorter.py

Author: squeaky-pl

pre_commit_hooks/file_contents_sorter.py

@@ -12,6 +12,7 @@
 from __future__ import print_function
 
 import argparse
+import sys
 from typing import IO
 from typing import Optional
 from typing import Sequence
@@ -53,3 +54,7 @@ def main(argv=None):  # type: (Optional[Sequence[str]]) -> int
             retv |= ret_for_file
 
     return retv
+
+
+if __name__ == '__main__':
+    sys.exit(main())