[core/module] better error reporting for failed module loads
[core/module] better error reporting for failed module loads

if a module fails to load, explicitly log errors for core and contrib in
the error log, but be a bit less verbose (and less confusing) in the
module error message itself.

fixes #747

tobi-wan-kenobi/bumblebee-status,tobi-wan-kenobi/bumblebee-status