Note: This is not required, it is backwards compatible so the old settings will still work.

Well, it crashes for me with an import exception without this update...

EDIT: how can it be backward compatible if the variable DATABASE doesn't exist anymore in the configuration.py? Or am I misunderstanding your comment?

Maybe you mean that for users who update netbox there is no need to update the configuration.py at all and then the DATABASE variable can be imported? But at least for people who do a fresh install or who also update the config this will not work anymore...

So maybe something like this is better? :)

# ...
-from .configuration import DATABASE
-DATABASES = DynamicSchemaDict({
-    'default': DATABASE,
-})
+try:
+  from .configuration import DATABASES
+  DATABASES = DynamicSchemaDict(DATABASES)
+except ImportError:
+  from .configuration import DATABASE
+  DATABASES = DynamicSchemaDict({
+      'default': DATABASE,
+  })
# ...

or the other way around: first trying to import DATABASE and if that fails trying DATABASES ...