Comment 2 for bug 497694

I may have mentioned it before, I think it could be a service which is provided by trace.py
Make a log level for annoying warning messages, so that this sort of functionality can be reused without much effort.
Callers can use it like:
trace.nag("deprecation_warnings", "Such and such is deprecated")
trace.nag("old_format", "You should upgrade your branch")

If the message is printed it should explain (or point you to a topic which explains)
how to disable a certain class of annoying error messages (by adding the class eg. "deprecation_warnings" somewhere in the config file).

my 2c