It would be possible for subprocess to replace "%1" with the filename parsed from the command line and then re-raise the exception. That said, it's not as if this is a deficiency in the Windows implementation relative to subprocess on POSIX. For example, in 3.4 on Linux it raises a generic ENOEXEC error:

    >>> os.access('./test.txt', os.X_OK)
    True
    >>> subprocess.call(['./test.txt'])
    Traceback (most recent call last):
      File "<stdin>", line 1, in <module>
      File "/usr/lib/python3.4/subprocess.py", line 537, in call
        with Popen(*popenargs, **kwargs) as p:
      File "/usr/lib/python3.4/subprocess.py", line 859, in __init__
        restore_signals, start_new_session)
      File "/usr/lib/python3.4/subprocess.py", line 1457, in _execute_child
        raise child_exception_type(errno_num, err_msg)
    OSError: [Errno 8] Exec format error

It could provide the filename, for example:

    >>> raise OSError(errno.ENOEXEC, os.strerror(errno.ENOEXEC), './test.txt')
    Traceback (most recent call last):
      File "<stdin>", line 1, in <module>
    OSError: [Errno 8] Exec format error: './test.txt'

A new issue should be raised to fix the FormatMessage calls in the standard library that mistakenly leave out FORMAT_MESSAGE_IGNORE_INSERTS.