I recently upgrading by CI2 application to use CI3 (currently 3.0.3). In my CI2 code I had extended the CI_Log core class with my own MY_Log class located under application/core. This worked fine in CI2 but since the upgrade to CI3 get_instance() using in my extended class always returns NULL.
Has something changed in the way extended core class get loaded?
UPDATE: Just to add some more context to this, this happens when CI runs into a 404 error.