Make phone number optional during member registration

website/registrations/migrations/0008_auto_20180704_2309.py

+# Generated by Django 2.0.2 on 2018-07-04 21:09
+
+import django.core.validators
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('registrations', '0007_change_registration_status_completed'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='registration',
+            name='phone_number',
+            field=models.CharField(blank=True, max_length=20, null=True, validators=[django.core.validators.RegexValidator(message='please enter a valid phone number', regex='^\\+?\\d+$')], verbose_name='phone number'),
+        ),
+    ]

website/registrations/models.py

@@ -164,7 +164,8 @@ class Registration(Entry):
             regex=r'^\+?\d+$',
             message=_('please enter a valid phone number'),
         )],
-        blank=False,
+        blank=True,
+        null=True,
     )
 
     # ---- University information -----