Bug in setup script

[jimboid]

The python version check simply issues a warning if the python version is out of scope, this should issue a warning and then fail.

Reported by Hannes Loeffler

[jimboid]

Changed the weak checking code for a list based check that we should keep up to date with the unit tests. New versions will fail the unit tests on travis if this is forgotten about so there is no dangers with this.