To allow people to use a keystoneauth session with keystoneclient we
need to make it so that any exceptions that keystoneclient catch are the
same as what keystoneauth might throw.
The only practical way to do this is to map the keystoneclient
exceptions onto the keystoneauth equivalents. This is fairly easy as all
these exceptions were extracted from keystoneclient initially.
Closes-Bug: #1515048
Change-Id: I3b74b0ba1e1f9dda937a2d90e2d75ff0b7597a9b
bdd44d3142