Always coloring 'async' and 'await' is trivial (augment expression and add test line) and acceptable to me.

I am a git neophyte and am waiting for workflow development to settle down before working on new setup for git.  If you want to submit the change for 3.6.1, go ahead. (But leave issue open.)  Otherwise, I will get it into 3.6.2 (and 3.7).  Patch is against 3.6 idlelib.colorize, but 3.7 is identical.

The test is to run colorizer.py as main module (python -m idlelib.colorize, or F5 in IDLE editor).  Click 'Test' button and check that 'async' and 'await' have same color as other keywords.  This cannot affect anything in test suite; colorizer is only used by turtledemo, which is not tested, and which will not notice anyway.