Small CLI cleanups

* yapf changes
* Fix the cformat test
* Make the normpath test work when run from /
* `qmk config`: Mark `--read-only` as arg_only

lib/python/qmk/tests/test_cli_commands.py

@@ -7,7 +7,7 @@ def check_subcommand(command, *args):
 
 
 def test_cformat():
-    assert check_subcommand('cformat', 'tmk_core/common/backlight.c').returncode == 0
+    assert check_subcommand('cformat', 'tmk_core/common/keyboard.c').returncode == 0
 
 
 def test_compile():