The journey-home guard counted every non-<module> frame in plugins_cmd*.py as
the migration running plugin-install code. d6813a5dd7 gave
plugins_cmd_install.py its first class statement (_ConsentRefusal), whose body
runs at import as a frame named after the class, so a plain import (via
plugins_cmd.py's module-level import) read as a call and the guard failed with
no change in what the update does: migrate_all_homes() still returns [] and
calls nothing in the module.
Frames called by their own file's <module> frame (class statements,
module-level comprehensions) are import-time execution and are skipped; a real
call into an install function is still recorded.
0d69d07bb2