tests: Allow changing modules path and adding to PYTHONPATH
tests: Allow changing modules path and adding to PYTHONPATH

This way run_tests.sh follows what local_run.sh can do.

laurent-george/weboob,willprice/weboob,frankrousseau/weboob,Konubinix/weboob,RouxRC/weboob,sputnick-dev/weboob,RouxRC/weboob,sputnick-dev/weboob,frankrousseau/weboob,nojhan/weboob-devel,nojhan/weboob-devel,Konubinix/weboob,frankrousseau/weboob,laurent-george/weboob,willprice/weboob,nojhan/weboob-devel,RouxRC/weboob,willprice/weboob,sputnick-dev/weboob,Konubinix/weboob,laurent-george/weboob