Use bundler/setup for more graceful bundler related failures, fixes #4222

# Validation

 - [ ] Add some bogus change to the appropriate section of ```Gemfile```, like bumping a version or adding some unrelated, uninstalled gem (try 'cats').
 - [ ] Run ```msfconsole```, confirm the failure mode is now different and better than before
 - [ ] Undo ```Gemfile``` changes, redo step 2