deposit.cli: Fix cli parsing issue when xml error is returned by server
Prior to this commit, any error returned by the deposit server would end up a cascading KeyError [1]
This commit fixes it.
I'm not sure whether we want to keep the existing behavior. I don't think that old code is possible to reach.
- [1] swh/meta$977
Test Plan
one test added
Migrated from D5298 (view on Phabricator)