Issues with Python 3 support

The system version of Python must match the version that Vim was compiled with. According to #17, the following outputs must match:

• python --version in a terminal, and
• :python3 import sys; print(sys.version) in Vim

For Win32, Vim binaries compiled with python3 support are provided at:

• https://github.com/vim/vim-win32-installer/releases
• https://tuxproject.de/projects/vim