Hello Andreas, it seems to me that the problem is due to the 2to3 conversion.
I looked at the first failure when you re-activate the unit test[1] to my opinion, the code is modify in place with 2to3. So the code on the source after the configuration is already converted to python3. And during the build process, with python2 the code is copied as it in the .pybuild place for python2 with python3 we see that the RefactoringTool, does nothing, it means the code is already converted to python3. So I guess that the pythoncode used for python2 is already the code modified for python3... this is why the code failed for the unit test. [1] https://salsa.debian.org/debian/python-uncertainties/-/jobs/53314
