Change the password of an existing user.

        :param username: the username who's password is being changed
        :type username: str
        :param password: the new password for the user
        :type password: str

def set_user_password(self, username, password):
        """Change the password of an existing user.

        :param username: the username who's password is being changed
        :type username: str
        :param password: the new password for the user
        :type password: str
        """
        text = "SET PASSWORD FOR {0} = {1}".format(
            quote_ident(username), quote_literal(password))
        self.query(text)