Remove unnecessary double printing of filename

pre_commit_hooks/pretty_format_json.py

@@ -120,12 +120,6 @@ def main(argv=None):  # type: (Optional[Sequence[str]]) -> int
             )
 
             if contents != pretty_contents:
-                print(
-                    'File {} is not pretty-formatted'.format(json_file),
-                    file=sys.stderr,
-                )
-                sys.stderr.flush()
-
                 if args.autofix:
                     _autofix(json_file, pretty_contents)
                 else:

tests/pretty_format_json_test.py

@@ -131,11 +131,9 @@ def test_diffing_output(capsys):
 +  "foo": "bar"
  }}
 '''.format(a, b)
-    expected_err = 'File {} is not pretty-formatted\n'.format(resource_path)
-
     actual_retval = main([resource_path])
     actual_out, actual_err = capsys.readouterr()
 
     assert actual_retval == expected_retval
     assert actual_out == expected_out
-    assert actual_err == expected_err
+    assert actual_err == ''