Catch ProcessExecutionError in revoke_cert

Catch processExecutionError if revoking the
certificate fails.

This change has been abandoned by Chuck Short, so
I am continuing where he left off (mattoliverau).

Continues abandoned change: 17741

Change-Id: I9714ea8cece87256ff5f9a936286c1da3d628af9
Closes-Bug: #883320
Co-Authored-By: chuck.short@canonical.com
Add API schema for v2.1/v3 aggregates API

By defining the API schema, it is possible to separate the validation
code from the API method. The API method can be more simple.
In addition, a response of API validation error can be consistent for
the whole Nova API.

Partially implements blueprint v3-api-schema

Change-Id: I67a1b723f37256e8bdfaf38d9f5ad0a4c4d2e53e
Merge "Catch ProcessExecutionError in revoke_cert"
Merge "Add API schema for v2.1/v3 aggregates API"