Do not make string nullable in database

users/migrations/0041_auto_20200923_2030.py

@@ -0,0 +1,25 @@
+# Generated by Django 2.2.12 on 2020-09-23 18:30
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('users', '0040_delete_clef'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='user',
+            name='address',
+            field=models.CharField(blank=True, default='', max_length=255, verbose_name='address'),
+            preserve_default=False,
+        ),
+        migrations.AlterField(
+            model_name='user',
+            name='telephone',
+            field=models.CharField(blank=True, default='', max_length=15, verbose_name='phone number'),
+            preserve_default=False,
+        ),
+    ]

users/models.py

@@ -13,13 +13,11 @@ class User(AbstractUser):
     telephone = models.CharField(
         verbose_name=_('phone number'),
         max_length=15,
-        null=True,
         blank=True,
     )
     address = models.CharField(
         verbose_name=_('address'),
         max_length=255,
-        null=True,
         blank=True,
     )
     maxemprunt = models.IntegerField(