Fix error handling logger method.
Fix error handling logger method.

The error handler on dispatch is swallowing exceptions and never raising SerializationError due to "AttributeError: '_TxaioLogWrapper' object has no attribute 'failure'" being fired in the exception handling routine.
oberstet/autobahn-python,tavendo/AutobahnPython,crossbario/autobahn-python,Jenselme/AutobahnPython,RyanHope/AutobahnPython,oberstet/autobahn-python,oberstet/autobahn-python,crossbario/autobahn-python,meejah/AutobahnPython,crossbario/autobahn-python