Parse a time from an ftp directory listing.

def _parse_ftp_time(cls, time_text):
        # type: (Text) -> Optional[int]
        """Parse a time from an ftp directory listing.
        """
        try:
            tm_year = int(time_text[0:4])
            tm_month = int(time_text[4:6])
            tm_day = int(time_text[6:8])
            tm_hour = int(time_text[8:10])
            tm_min = int(time_text[10:12])
            tm_sec = int(time_text[12:14])
        except ValueError:
            return None
        epoch_time = calendar.timegm(
            (tm_year, tm_month, tm_day, tm_hour, tm_min, tm_sec)
        )
        return epoch_time