Error with Scripting Vim in Python - Ubuntu Xenial

While updating to Ubuntu 16.04 (Xenial Xerus) my .vimrc stopped working with the following error message:

    vim.error: Vim(python):E319: Sorry, the command is not available
    in this version: python << endpython

After a bit of wrestling I found out that you have to replace

    python << endpython


    python3 << endpython

The big tell was that $ vim --version yielded, among other things, -python and +python3.