Message 294845 - Python tracker

Oh, it's my fault: it's a bug coming from FASTCALL optimizations. The strange thing is that the bug wasn't catched by the giant Python test suite :-(

I knew that _PyStack_UnpackDict() has a bug in Python 3.6, but I completely forgot to fix it :-(

https://github.com/python/cpython/pull/1886 fixes the bug, but has not test yet.