The warning displayed when an INavigationContributor fails has changed:
Error with navigation contributor "WikiModule"
WikiModule failed with TracError: You did wrong!
The exception is still logged at warning level for TracError and error level with traceback otherwise. The main change is that we don't specify to the user that the error came from a "navigation contributor", but that doesn't seem important anyway.
Similar behavior for timeline event providers, however failing event providers are skipped and add a warning, rather than rendering a TracError in the timeline.