Some small exception cleanups
Some small exception cleanups

Whitespace change and compare directly
to none since user exceptions may have
overloaded the boolean operator and
avoid checking the exception classes
if the input is empty in the first place.

Change-Id: I426741bbc23181e96084383eaf77daa1d612ab59

jimbobhickville/taskflow,varunarya10/taskflow,citrix-openstack-build/taskflow,varunarya10/taskflow,jimbobhickville/taskflow,junneyang/taskflow,openstack/taskflow,pombredanne/taskflow-1,openstack/taskflow,citrix-openstack-build/taskflow,junneyang/taskflow,pombredanne/taskflow-1