Add a new exception for invalid structure
Add a new exception for invalid structure

This commit fixes too broad exception in output_parser. Otherwise, we
can't assert the Exception in unit tests.

Partially implements bp unit-tests

Change-Id: I9e45571dbf964a37dd9d0249a6f662216d5d046c

cneill/tempest-lib,mtreinish/tempest-lib,varunarya10/tempest-lib,sorenh/tempest-lib,JioCloud/tempest-lib,afaheem88/tempest-lib