Codestyle fixes (flake8)

This also adds the flake8 dependencies to the test extras for
installation.

tests/unit/test_models.py

@@ -10,25 +10,30 @@ from wagtail_factories import SiteFactory
 
 from wagtail_personalisation import rules
 
-"""Time Rule tests"""
+
+# Time Rule tests
+
 @freeze_time("10:00:00")
 def test_create_time_rule():
     time_rule = rules.TimeRule(start_time=datetime.time(8, 0, 0), end_time=datetime.time(23, 0, 0))
 
     assert time_rule.test_user() is True
 
+
 @freeze_time("10:00:00")
 def test_time_rule_false():
     time_rule = rules.TimeRule(start_time=datetime.time(11, 0, 0), end_time=datetime.time(23, 0, 0))
 
     assert time_rule.test_user() is False
 
+
 @freeze_time("10:00:00")
 def test_time_rule_reverse():
     time_rule = rules.TimeRule(start_time=datetime.time(13, 0, 0), end_time=datetime.time(9, 0, 0))
 
     assert time_rule.test_user() is False
 
+
 @freeze_time("10:00:00")
 def test_time_rule_reverse_next_day():
     time_rule = rules.TimeRule(start_time=datetime.time(11, 0, 0), end_time=datetime.time(11, 0, 0))
@@ -36,12 +41,13 @@ def test_time_rule_reverse_next_day():
     assert time_rule.test_user() is False
 
 
-"""Visit Count Rule tests"""
+# Visit Count Rule tests
 def test_visit_count_rule():
-    visit_count_rule = rules.VisitCountRule()
+    rules.VisitCountRule()
 
 
-"""Test test"""
+# Test test
+
 @pytest.mark.django_db
 def test_test(rf):
     site = SiteFactory()