release: Revamp to use subprocess instead of os.system
release: Revamp to use subprocess instead of os.system

Signed-off-by: James McCoy <91ae71a1168cea0b65ac9975da69d5a7753116be@users.sourceforge.net>

jeffmahoney/supybot,buildbot/supybot,Ban3/Limnoria,frumiousbandersnatch/supybot-code,ProgVal/Limnoria-test,haxwithaxe/supybot,ProgVal/Limnoria-test,Ban3/Limnoria