The errror, "RuntimeError: Objects in this class cannot be updated outside an edit session" occurs even though operation succeeded when running arcpy.da.ExtendTable against a feature layer participating in a composite relationship class.
Last Published: December 15, 2015ArcSDE/Enterprise Geodatabase
Bug ID Number
August 31, 2015
January 28, 2021
The bug has been fixed. See the Version Fixed and Additional Information, if applicable, for more information.