Since Python 2.6, it seems the documentation is in the new reStructuredText format, and it doesn\'t seem very easy to build a Texinfo Info file out of the box anymore.
The Ubuntu distribution provides packages pythonX.Y-doc (which include the documentation in Info format) at least since 18.04 (bionic); in 19.04 X.Y stands for 2.7, 3.7 and 3.8. The package does not have many dependencies, I assume it is possible to install it in other distributions too.