Open ArcCatalog and all tools within Python Toolbox(pyt) have a red-x error next to them claiming that "Arcpy module has no attribute Parameter"
Delete ArcToolbox.dat file in ~\AppData\Roaming\ESRI\Desktop10.2\ArcToolbox
Open ArcCatalog, everything is fine with tools
Run tools successfully
GOTO Symptom 1 .....
Seems like something in the geoprocessing results history is going wrong.
Any ideas for fixes?
I also want to maintain geoprocessing result history.