Issue importing settings since 3.2.3

[jaredahern]

Hello! I have a Django project in which I import the PANELS_DEFAULTS into the settings, modify it, and use it for DEBUG_TOOLBAR_PANELS. This simplifies the removal of any particular panel, as the defaults don't need to be hard-coded in our settings.

However, as of djdt 3.2.3, this no longer works. The following line in our settings.py file causes an AppRegistryNotReady error:

from debug_toolbar.settings import PANELS_DEFAULTS

If we change it to import debug_toolbar, I see an ImproperlyConfigured error related to missing SECRET_KEY.

I think this is because as of 3.2.3, debug_toolbar/__init__.py imports app_name, which ultimately imports the whole package. And perhaps that's not good to do that in a settings.py file. It might be that we can restructure our settings.py to make this work, but at the moment I'm guessing not.

Would it be possible to restructure things such that debug_toolbar.settings could be imported without triggering the import of other submodules? Perhaps put app_name by itself in a module that itself doesn't import anything? I'm happy to task a stab at this if someone indicates that it would be acceptable.

Or perhaps is there a different approach to "modifying" the default panel settings?

[matthiask]

I noticed too that somehow more of the toolbar was imported earlier than previously.

I think there's no harm duplicating this string in both modules and keeping it synchronized. I submitted a PR.