check-code: add a rules to catch os.path.abspath...
check-code: add a rules to catch os.path.abspath
All previous usages have been migrated. So let us add a check-code rules to
catch future usages.
We restrict it to mercurial/ and hgext/ because multiple other script never
depends on Mercurial modules.
Differential Revision:
https://phab.mercurial-scm.org/D11072
