Fetch the user from the database

            The function will return None if the user is not found

def get_user(self, username):
        """ Fetch the user from the database

            The function will return None if the user is not found
        """

        sql = '''SELECT * FROM user WHERE username = ?'''
        self._db_curs.execute(sql, (username, ))
        user = self._db_curs.fetchone()
        return user