sort imports using isort. tested.

core/TESTS/tests_caves.py

@@ -2,11 +2,14 @@
 Modified for Expo April 2021.
 """
 
-import unittest
 import re
-from django.test import TestCase, SimpleTestCase, Client
+import unittest
+
+from django.test import Client, SimpleTestCase, TestCase
+
+from troggle.core.models.caves import Area, Cave
 from troggle.core.models.troggle import Expedition, Person, PersonExpedition
-from troggle.core.models.caves import Cave, Area
+
 
 class FixtureTests(TestCase):
     '''These just hit the database.