I am have a script using the following:
pythonaddins.GPToolDialog(r'C:\Program Files (x86)\ArcGIS\Desktop10.2\ArcToolbox\Toolboxes\Data Management Tools.tbx', 'Merge')
and it throws the 001156 error. When I physically run the merge tool out of ArcToolbox on the same layers it runs fine, also I know for a fact the 2 layers to be merged are exactly the same.
Any ideas are welcome.