add DESGW to EMGroups (see #5695)

gracedb/migrations/0023_add_DESGW_to_EMGroups.py

+# -*- coding: utf-8 -*-
+from __future__ import unicode_literals
+
+from django.db import migrations, models
+
+GROUP_NAME = "DESGW"
+
+def add_group(apps, schema_editor):
+    EMGroup = apps.get_model('gracedb','EMGroup')
+    grp, created = EMGroup.objects.get_or_create(name=GROUP_NAME)
+    if created:
+        grp.save()
+
+def remove_group(apps, schema_editor):
+    EMGroup = apps.get_model('gracedb','EMGroup')
+    EMGroup.objects.get(name=GROUP_NAME).delete()
+
+class Migration(migrations.Migration):
+
+    dependencies = [ 
+        ('gracedb', '0022_add_O2VirgoTest_search'),
+    ]   
+
+    operations = [ 
+        migrations.RunPython(add_group, remove_group),
+    ]