[validation error] refactor validation error handling so translation is done on the web side Users should now use cubicweb.validation_error helper function that will activate the feature with other handy behaviours. Also test testing for message in errors should call exception.tr(unicode) before comparing. Using bare ValidationError keep backward compat.

+
−sql('DROP FUNCTION IF EXISTS _fsopen(bytea)')
+
−sql('DROP FUNCTION IF EXISTS fspath(bigint, text, text)')