Installed this and now I can no longer use Wagtail admin

[serl]

Seems like the devs at Wagtail are not using fastdev!

While I'll check with them to fix the undefined tag, I'm sure that's not the only exception.
It would be great if we could exclude specific apps (or directly all external code), with a configuration or something.

TLDR: I think that fastdev should not run outside of the project's boundaries.

Longer explanation: while I totally agree on the fact that undefined variables must explode as they always do everywhere else, I feel that the Django templating language is meant to be more permissive. For me, that simply means that we could find ourselves adding apps to our projects which are written by people not sharing our same views on undefined variables, and are not willing to "fix" what is not a problem to them.

[boxed]

Yea, maybe a simple whitelist that is regexes on template names will do. I'm open to a PR for this.