Currently shipyard raises same error for 2 scenarios-
- Collection empty or resulted in no revision (Error code - 400)
- Buffer is either not empty or the collection already
exists in buffer (Error code - 409)
This PS enables shipyard to raise specific errors for the above
given scenarios which would equip consumers of Shipyard API client
to handle the exception gracefully.
Change-Id: I10860ca60f4fde4088cbb146283a2db305418320