Mongoid, MongoDB Ruby Driver, and BSON Ruby are loading a gem called "rspec-mocks-diag".

This is an out-of-date hack of the rspec-mocks gem which adds additional logging. It was done my a former MongoDB employee. The gem appears to still be under the former employee's control, i.e. not released officially by MongoDB. Fortunately the gem is not loaded in production, but certainly this goes against security best practices and should be cleaned up on all projects where it's used.