[test] Use python3 for test wrappers
We don't need to support Python 2 anymore (not officially supported anymore since this year). New systems might only have Python3 such as Ubuntu 20.04LTS now used for the buildbot testing.
Needs backport to 3.2.
We don't need to support Python 2 anymore (not officially supported anymore since this year). New systems might only have Python3 such as Ubuntu 20.04LTS now used for the buildbot testing.
Needs backport to 3.2.