A decorator that registers a coroutine as a local error handler.

        A local error handler is an :func:`.on_command_error` event limited to
        a single command. However, the :func:`.on_command_error` is still
        invoked afterwards as the catch-all.

        Parameters
        -----------
        coro: :ref:`coroutine <coroutine>`
            The coroutine to register as the local error handler.

        Raises
        -------
        TypeError
            The coroutine passed is not actually a coroutine.

def error(self, coro):
        """A decorator that registers a coroutine as a local error handler.

        A local error handler is an :func:`.on_command_error` event limited to
        a single command. However, the :func:`.on_command_error` is still
        invoked afterwards as the catch-all.

        Parameters
        -----------
        coro: :ref:`coroutine <coroutine>`
            The coroutine to register as the local error handler.

        Raises
        -------
        TypeError
            The coroutine passed is not actually a coroutine.
        """

        if not asyncio.iscoroutinefunction(coro):
            raise TypeError('The error handler must be a coroutine.')

        self.on_error = coro
        return coro