[web] Return useful error messages when exceptions arise in ajax controllers (closes #3932503)
The call to super() in RemoteCallException passes 'reason' all the way to
python's Exception.__init__() which is then stored in Exception.args. This way,
CubicWebPublisher.ajax_error_handler() gets a useful error message when calling
unicode(exc).
The change to uilib is just to prepend the exception type name. Just a small
improvement.
usr/lib/PY_VERSION/*-packages/cubicweb/devtools/
usr/lib/PY_VERSION/*-packages/cubicweb/skeleton/
usr/lib/PY_VERSION/*-packages/cubicweb/test
usr/lib/PY_VERSION/*-packages/cubicweb/entities/test
usr/lib/PY_VERSION/*-packages/cubicweb/ext/test
usr/lib/PY_VERSION/*-packages/cubicweb/server/test
usr/lib/PY_VERSION/*-packages/cubicweb/sobjects/test
usr/lib/PY_VERSION/*-packages/cubicweb/hooks/test
usr/lib/PY_VERSION/*-packages/cubicweb/web/test
usr/lib/PY_VERSION/*-packages/cubicweb/etwist/test