Print correct validation errors

This pull-request should close issues #773, #826, #913, #652, #677, #769, #932, #799

After sifting through the code, I realized all the functionality was already there. My guess is that either this bug was introduced recently due to a big change, or that the functionality was recently added but hadn't been propagated to the controller hooks.

I created the patch against the development branch, but I can also rebase it to master if preferred.