Fix constraint in migration

aleksis/core/migrations/0071_constrain_calendar_event_starting_before_ending.py

@@ -16,7 +16,7 @@ class Migration(migrations.Migration):
         ),
         migrations.AddConstraint(
             model_name='calendarevent',
-            constraint=models.CheckConstraint(check=Q(date_end__gt=F('date_start')),
+            constraint=models.CheckConstraint(check=Q(date_end__gte=F('date_start')),
                                               name="date_start_before_end"
             ),
         ),

aleksis/core/tests/regression/test_regression.py

@@ -7,7 +7,7 @@ from django.urls import reverse
 
 import pytest
 
-from aleksis.core.models import Holiday, Group, OAuthApplication, Person
+from aleksis.core.models import Group, Holiday, OAuthApplication, Person
 
 pytestmark = pytest.mark.django_db