async def _file_to_mxc_url(self, file_event):
    """Given a file event, return the mxc URL."""
    uploaded = False
    mxc_url = None
    file_dict = None
    if file_event.url:
        url = urlparse(file_event.url)
        if url.scheme == "mxc":
            mxc_url = file_event.url

    if not mxc_url:
        encrypt_file = (
            self._allow_encryption
            and file_event.target in self.connection.store.load_encrypted_rooms()
        )
        upload_file = await file_event.get_file_bytes()
        mimetype = await file_event.get_mimetype()

        response = await self.connection.upload(
            lambda x, y: upload_file, content_type=mimetype, encrypt=encrypt_file
        )

        if len(response) >= 2:
            response, file_dict = response
        else:
            response = None
            file_dict = None