Add error handler for OMDB request, only do request if a query is passed.
Refactor tests: add a addItems method to base test case.

Makes it easier to add items to the database for testing. Return a list
of the ids of the newly created objects.
Refactor tests: Add a assertValidClientError method.

This checks that the reponse is a good response to client errors,
verifying status code, that the message is good, and that a list of
errors is included.
Refactor tests: add assertValidCreate helper.

Check for 201, a msg, and that the resulting object has an ID field.
Make sure tests use normal log handlers.

Helps a lot when debugging failing tests to actually have the error log.

Added a test_log_conf.yaml to complete this.