[web] fix #724769: Use RemoteCallFailed in the publisher's error_handler On json_request, errors handled by the publisher should raise RemoteCallFailed exceptions instead of standard StatusResponse so that errbacks get called normally on the client side.

This directory is where you should put your lax components.

For your application to actually use a component, you also 
have to modify the ``INCLUDED_COMPONENTS`` variable in 
the ``custom.py`` module.