Updated setup.py to better handle missing packages.
Updated setup.py to better handle missing packages.

mandx/pyrax,0dataloss/pyrax,naemono/pyrax,ddaeschler/pyrax,roelvv/pyrax,sivel/pyrax,EdLeafe/pyrax,opsdisk/pyrax,briancurtin/pyrax,rackspace/pyrax,vikomall/pyrax,pratikmallya/pyrax,rackerlabs/heat-pyrax,emonty/pyos