HPCC-10741 Regression suite is dependent on minimum python version, it should
check at start up.

Add code to check version of the installed Python system.
Add Python version related note into README.rst
Add initialisation to some local variables.

Signed-off-by: Attila Vamos <attila.vamos@gmail.com>
Merge pull request #5307 from AttilaVamos/HPCC-10741-improvement

HPCC-10741 Regression suite is dependent on minimum python version, it should  check at start up.

Reviewed-By: Richard Chapman <rchapman@hpccsystems.com>