The type of the python_version variable matters when we interpret it
after yaml deserialization. If it is interpreted as a float then 3.1 ==
3.10 and those python versions are very different. Instead make note
that it should be a string and then update all of the tox jobs to set
this variable as a string.
Change-Id: I55bbc70526a13e6bd4c3c32da8590ad2af76fe7c
52e84220e5