Tweak "add to world" prompt, bug #455946.
emerge --sync: python 2.6.4 compat, bug #456236

Avoid "TypeError: keywords must be strings" issue triggered
by unicode_literals: http://bugs.python.org/issue4978

Also see commit e9a04922c144b267534e3335d2ff3d7bb8994b80.
Fix some ResourceWarnings.
Avoid using gawk, where generic awk is enough
Trigger rebuild for sub-slot change, bug #456208.

If sub-slot changes without a revbump, trigger a rebuild so that
dependent packages will have the new sub-slot recorded in their
slot-operator deps. Hopefully this will fix bug #456208.
_slot_change_probe: handle masks
deprecated_profile_check: suggest portage upgrade

If the new profile can't be parsed due to unsupported EAPI, then show a
warning like this:

!!! Your current profile is deprecated and not supported anymore.
!!! Use eselect profile to update your profile.
!!! Please upgrade to the following profile if possible:
        default/linux/x86/13.0/desktop

!!! Unable to parse profile: '/usr/portage/profiles/default/linux/x86/13.0/desktop'
!!! ParseError: Profile contains unsupported EAPI '5': '/usr/portage/profiles/eapi-5-files/eapi'

 * You must update portage before you can migrate to the above profile.
 * In order to update portage, run 'emerge --oneshot portage'.