Code review comment for lp:~nmb/brz/warn-bazaar-directory

There are two complicating factors here that this change does address:

* We don't want to do all the work to load config each time this function is called
* We still need a generic don't multiply warn for various things

As a concrete suggestion, I think a better choice is storing the config on global state rather than having a warning_printed attr, which will also happen to make any warning only appear once.

Is there any reason to refresh the config dir mid process execution?