WIP: Add unit tests for UsageService behavior

The ModuleUsageTest fails, because the DefaultEventService is not yet
initialized, despite its high priority. This prevents the
DefaultUsageService event handler from getting registered as it should.
DefaultModuleService: include exception in log

When logging the error creating a module, include the exception too.

We have it, so we should pass it on. (If the stack trace is annoying
on the console, the answer is not to eat the exception, but rather
to change on information from the log is emitted to the console.)