use my.config instead of mycfg; minor cleanups and docstrings

tox.ini

@@ -6,12 +6,13 @@ skip_missing_interpreters = True
 # TODO ugh. unclear how to reuse setup.cfg deps in tox
 [testenv]
 passenv = CI CI_* CIRCLE*
-setenv = MY_CONFIG = mycfg_template
+# deliberately set to nonexistent pathe to check the fallback logic
+setenv = MY_CONFIG = nonexistent
 commands =
     pip install -e .
     # TODO ??
     # python -m pytest {posargs}
-    python3 -c 'import my.init; import my.config; print(my.config.__path__)'
+    python3 -c 'import my.init; from my.config import stub as config; print(config.key)'
     python3 -c 'import my.init; import my.config; import my.config.repos' # shouldn't fail at least
     # TODO run demo.py? just make sure with_my is a bit cleverer?
     # TODO e.g. under CI, rely on installing
@@ -22,7 +23,7 @@ commands =
 changedir = {toxworkdir}/{envname}/../..
 # TODO not sure?? also reuse installed my. instead on installing in demo.py?
 skip_install = true
-# TODO need to keep full mycfg.py as example? to dummy run CI
+# TODO need to keep full config as example? to dummy run CI
 commands = ./demo.py