When RESTXQ detects a security error, it should not fail with a 500.
Instead initiate a basic auth handshake (401), so that the
user can retry the request with the correct level or authorisation.
Use the existing authenticator, instead of cooking up a new one.
Merge pull request #133 from Infiniverse/fix-restxq-401

When RESTXQ detects a security error, it should not fail with a 500.