Raise DevopsEnvironmentError, if admin node role does not exist
Raise DevopsEnvironmentError, if admin node role does not exist

Raise DevopsEnvironmentError, if admin node role does not exist,
as opposite to throw IndexError (it's does not informative)

Change-Id: Idb1d040833298ed240add82229c03c1e6870e8a8
(cherry picked from commit a771e85)

stackforge/fuel-devops,stackforge/fuel-devops