Error messages returned to the user are not consistent across all apis

[Pranali Deore]

Error messages returned to the user are not consistent across all apis in case of all exceptions derived from NotFound exception,
e.g., VolumeNotFound, SnapshotNotFound etc.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/186688

[Rajesh Tailor (rajesh-tailor)]

This issue is in nova project as well, where generic NotFound exception is raised instead of Specific NotFound exception.
for eg. InstanceNotFound, VolumeNotFound, ImageNotFound etc.

[Sean Dague (sdague)]

I feel like this is one of those things where we need the API working group error specification and can move on from there. Pattern matching on exception names (which might change), isn't really a good long term plan.