Google AppEngine docs is inconsistent at this point.
It offers a download of AppEngineLauncher for OS X rather than AppEngine. Installing that does NOT, per docs, put appcfg.py or dev_appserver.py in the path.
It does create instances of those.
Directly invoking dev_appserver.py works; modulo a warning in importing PIL; that seems OK.
I see two instances of appcfg.py: in Applications/GoogleAppEngineLauncher.app//Contents/Resources :
Neither works. They both say ImportError: No module named google. I have deployed test code effectively. I don't actually know what appcfg is supposed to do.