Sometimes an error and the error message are different things. One of the examples is that my wxpython-program did not want to start after converting to exe using pyinstaller:
ImportError: No module named _core_
The two confusing things for me were:
* Some time ago the exe-version worked
* There is a file wx._core_.pyd in the program's directory
And a minimal test example worked again!
After some meditation, the root of the problem was found:
More precisely, "reload" does not work with PyInstaller. At the moment I don't know a good solution and just have commented out the problem line.