'overriding' is misspelled as 'overridding' in the Portage Eclass Warning when using overlays.
"It is best to avoid overridding eclasses from PORTDIR because it will trigger invalidation..."
Steps to Reproduce:
1. Install layman and add an overlay (i use mozilla and ruby)
2. Add 'source /etc/portage/local/layman/make.conf' to /etc/make.conf as instructed
3. Run emerge command (i.e. emerge -va ruby)
Thanks, this is fixed in 2.2_rc9.