Show an appropriate error when trying to load an uninstalled extension.
Review Request #7855 — Created Jan. 7, 2016 and submitted — Latest diff uploaded
When an extension is uninstalled, we still have the entry in the database with the configuration for that extension. However, since it couldn't be loaded, we try to show an error message, but never get far enough to compute one. We now have a suitable error in the API in the case where the extension class doesn't exist, saying that the extension isn't installed. This will help with this confusing error state.
Loaded my extension list and saw reasonable error messages, instead of
a blank error.