Fix an issue with repeatability of the sample_data command

The sample_data management command fails when run twice. The script
should be idempotent in nature

Author: palnabarun

junction/conferences/management/commands/sample_data.py

@@ -214,7 +214,7 @@ def create_user(self, counter=None, username=None, email=None, **kwargs):
             "is_superuser": kwargs.get('is_superuser', False),
             "is_staff": kwargs.get('is_staff', kwargs.get('is_superuser', self.sd.boolean())),
         }
-        user = get_user_model().objects.create(**params)
+        user, _ = get_user_model().objects.get_or_create(**params)
         password = '123123'
 
         user.set_password(password)