Remove user from the SQLite database.

            * `username` [string]
                Username of user to remove.

def remove_user(self, username):
        """ Remove user from the SQLite database.

            * `username` [string]
                Username of user to remove.
        """

        sql = '''DELETE FROM user WHERE username = ?'''
        try:
            self._db_curs.execute(sql, (username, ))
            self._db_conn.commit()
        except (sqlite3.OperationalError, sqlite3.IntegrityError) as error:
            raise AuthError(error)
        return self._db_curs.rowcount