In pysnmp/proto/mpmod/frc3412.py is a dictionary with well known error oids implemented (_snmpErrors).
Any oid not defined in this dictionary creates the default text 'errorReportReceived', the oid itself gets lost.
It would be helpful to add the oid to this text, eg.
varBinds, 'errorReportReceived %r'%(varBinds,)
This helps a lot for debugging. It is never a good idea to throw away valuable information.