It was found to be useless in [1].
It is one of distro_python_version usages.
Note Freezer and Horizon still use python_path (and hence
distro_python_version) for different purposes.
[1] https://review.opendev.org/675822
Change-Id: I6d6d9fdf4c28cb2b686d548955108c994b685bb1
Partially-Implements: blueprint drop-distro-python-version
9c38a0c77b