def get_dir_from_zipfile(zip_file, fallback=None):
    """Return the name of the root folder in a zip file.

    :param zip_file: a :class:`zipfile.ZipFile` instance.
    :param fallback: if `None`, the name of the zip file is used. This is
        returned if the zip file contains more than one top-level directory,
        or none at all.
    """
    fallback = fallback or zip_file.filename
    directories = [name for name in zip_file.namelist() if name.endswith("/")
                   and len(PurePath(name).parts) == 1]
    return fallback if len(directories) > 1 else directories[0]
def system_error(self,
                     error_msg,
                     error_code="",
                     reviewing_user=None,
                     reviewing_service=""):
        """
        Mark that this attempt could not be completed because of a system error.
        Status should be moved to `must_retry`. For example, if Software Secure
        reported to us that they couldn't process our submission because they
        couldn't decrypt the image we sent.
        """
        if self.status in ["approved", "denied"]:
            return  # If we were already approved or denied, just leave it.

        self.error_msg = error_msg
        self.error_code = error_code
        self.reviewing_user = reviewing_user
        self.reviewing_service = reviewing_service
        self.status = "must_retry"
        self.save()