Development: fix unreachable code around assertRaises blocks (#11365)

* tests: general cleanup and fixes for runnning under docker

This now allows tests to be run under a locally built or production
docker image with something like:

  `docker run --rm -v $PWD:/usr/src/paperless --entrypoint=bash paperlessngx/paperless-ngx:latest -c "uv run pytest"`

Specific fixes:
- fix unreachable code around `assertRaises` blocks
- fix `assertInt` typos
- fix `str(e)` vs `str(e.exception)` issues
- skip permission-based checks when root (in a docker container)
- catch `OSError` problems when instantiating `INotify` and
  skip inotify-based tests when it's unavailable.

* Reverts most files to dev while keeping the exception assert fixes

---------

Co-authored-by: Trenton H <797416+stumpylog@users.noreply.github.com>

src/documents/tests/test_management_exporter.py

@@ -571,7 +571,7 @@ class TestExportImport(
         with self.assertRaises(CommandError) as e:
             call_command(*args)
 
-            self.assertEqual("That path isn't a directory", str(e))
+        self.assertEqual("That path doesn't exist", str(e.exception))
 
     def test_export_target_exists_but_is_file(self):
         """
@@ -589,7 +589,7 @@ class TestExportImport(
             with self.assertRaises(CommandError) as e:
                 call_command(*args)
 
-                self.assertEqual("That path isn't a directory", str(e))
+            self.assertEqual("That path isn't a directory", str(e.exception))
 
     def test_export_target_not_writable(self):
         """
@@ -608,7 +608,10 @@ class TestExportImport(
             with self.assertRaises(CommandError) as e:
                 call_command(*args)
 
-                self.assertEqual("That path doesn't appear to be writable", str(e))
+            self.assertEqual(
+                "That path doesn't appear to be writable",
+                str(e.exception),
+            )
 
     def test_no_archive(self):
         """