helper function to generate a md5 hash of the swagger definition file
    any extra argument passed to the function is converted to a string
    and participates in the hash calculation

def _gen_md5_filehash(fname, *args):
    '''
    helper function to generate a md5 hash of the swagger definition file
    any extra argument passed to the function is converted to a string
    and participates in the hash calculation
    '''
    _hash = hashlib.md5()
    with salt.utils.files.fopen(fname, 'rb') as f:
        for chunk in iter(lambda: f.read(4096), b''):
            _hash.update(chunk)

    for extra_arg in args:
        _hash.update(six.b(str(extra_arg)))
    return _hash.hexdigest()