"script" language without a shebang causes unexpected OSError

[chriselion]

Repro steps:
Create a script hook.

-   repo: local
    hooks:
    -   id: foo
        name: foo
        language: script
        entry: foo.py
        types: [python]

foo.py can be empty.

If foo.py is not executable, pre-commit run foo --all-files produces a reasonable error message:

foo......................................................................Failed
- hook id: foo
- exit code: 1

Executable `/[redacted]/foo.py` is not executable

However, if it is executable but doesn't not contain a shebang, you get

$ pre-commit run foo --all-files
foo......................................................................An unexpected error has occurred: OSError: [Errno 8] Exec format error: '/[redacted]/foo.py'
Check the log at /[redacted]/.cache/pre-commit/pre-commit.log

Log contents:

version information

pre-commit version: 2.1.1
sys.version:
    3.7.6 (default, Dec 30 2019, 19:38:28) 
    [Clang 11.0.0 (clang-1100.0.33.16)]
sys.executable: /[redacted]/venv/bin/python3
os.name: posix
sys.platform: darwin

error information

An unexpected error has occurred: OSError: [Errno 8] Exec format error: '/[redacted]/foo.py'

Traceback (most recent call last):
  File "/[redacted]/venv/lib/python3.7/site-packages/pre_commit/error_handler.py", line 54, in error_handler
    yield
  File "/[redacted]/venv/lib/python3.7/site-packages/pre_commit/main.py", line 371, in main
    return run(args.config, store, args)
  File "/[redacted]/venv/lib/python3.7/site-packages/pre_commit/commands/run.py", line 339, in run
    return _run_hooks(config, hooks, args, environ)
  File "/[redacted]/venv/lib/python3.7/site-packages/pre_commit/commands/run.py", line 249, in _run_hooks
    verbose=args.verbose, use_color=args.color,
  File "/[redacted]/venv/lib/python3.7/site-packages/pre_commit/commands/run.py", line 165, in _run_single_hook
    retcode, out = language.run_hook(hook, filenames, use_color)
  File "/[redacted]/venv/lib/python3.7/site-packages/pre_commit/languages/script.py", line 19, in run_hook
    return helpers.run_xargs(hook, cmd, file_args, color=color)
  File "/[redacted]/venv/lib/python3.7/site-packages/pre_commit/languages/helpers.py", line 109, in run_xargs
    return xargs(cmd, file_args, **kwargs)
  File "/[redacted]/venv/lib/python3.7/site-packages/pre_commit/xargs.py", line 153, in xargs
    for proc_retcode, proc_out, _ in results:
  File "/usr/local/Cellar/python/3.7.6_1/Frameworks/Python.framework/Versions/3.7/lib/python3.7/concurrent/futures/_base.py", line 598, in result_iterator
    yield fs.pop().result()
  File "/usr/local/Cellar/python/3.7.6_1/Frameworks/Python.framework/Versions/3.7/lib/python3.7/concurrent/futures/_base.py", line 428, in result
    return self.__get_result()
  File "/usr/local/Cellar/python/3.7.6_1/Frameworks/Python.framework/Versions/3.7/lib/python3.7/concurrent/futures/_base.py", line 384, in __get_result
    raise self._exception
  File "/usr/local/Cellar/python/3.7.6_1/Frameworks/Python.framework/Versions/3.7/lib/python3.7/concurrent/futures/thread.py", line 57, in run
    result = self.fn(*self.args, **self.kwargs)
  File "/[redacted]/venv/lib/python3.7/site-packages/pre_commit/xargs.py", line 146, in run_cmd_partition
    *run_cmd, retcode=None, stderr=subprocess.STDOUT, **kwargs,
  File "/[redacted]/venv/lib/python3.7/site-packages/pre_commit/util.py", line 208, in cmd_output_p
    proc = subprocess.Popen(cmd, **kwargs)
  File "/usr/local/Cellar/python/3.7.6_1/Frameworks/Python.framework/Versions/3.7/lib/python3.7/subprocess.py", line 800, in __init__
    restore_signals, start_new_session)
  File "/usr/local/Cellar/python/3.7.6_1/Frameworks/Python.framework/Versions/3.7/lib/python3.7/subprocess.py", line 1551, in _execute_child
    raise child_exception_type(errno_num, err_msg, err_filename)
OSError: [Errno 8] Exec format error: '/[redacted]/foo.py'

[chriselion]

FWIW, I have identify==1.4.11 installed. here's what it returns for that file:

$ python -c "from identify.identify import parse_shebang_from_file; print(parse_shebang_from_file(\"foo.py\"))"
()

[asottile]

this has landed in 2.2.0 -- thanks again for the issue!