Fixes #537 - Avoid migration errors with custom user models

Author: claudep

two_factor/migrations/0003_auto_20150817_1733.py

@@ -10,18 +10,17 @@
 def migrate_phone_numbers(apps, schema_editor):
     PhoneDevice = apps.get_model("two_factor", "PhoneDevice")
     for device in PhoneDevice.objects.all():
-        username = device.user.get_username()
         try:
             number = phonenumbers.parse(device.number)
             if not phonenumbers.is_valid_number(number):
-                logger.info("User '%s' has an invalid phone number '%s'." % (username, device.number))
+                logger.info("User '%s' has an invalid phone number '%s'." % (device.user, device.number))
             device.number = phonenumbers.format_number(number, phonenumbers.PhoneNumberFormat.E164)
             device.save()
         except phonenumbers.NumberParseException as e:
             # Do not modify/delete the device, as it worked before. However this might result in issues elsewhere,
             # so do log a warning.
             logger.warning("User '%s' has an invalid phone number '%s': %s. Please resolve this issue, "
-                           "as it might result in errors." % (username, device.number, e))
+                           "as it might result in errors." % (device.user, device.number, e))
 
 
 class Migration(migrations.Migration):