We are currently solving the following issue within our repository. Here is the issue text:
--- BEGIN ISSUE ---
Django 2.1 upgrade
https://docs.djangoproject.com/en/2.1/releases/2.1/

There is a guide for upgrading: https://docs.djangoproject.com/en/2.1/howto/upgrade-version/

Basically
* Read the release notes
* update dependencies
* run tests with `python -Wa` and solve deprecation warnings
* put the new django into the requirements
* run tests, fix failures if any
* run tests with `python -Wa` and solve deprecation warnings again
* if there was any new feature in the release notes that might help us, use it

also, we need to check the installed python version on production, django 2.1 supports python 3.5 and newer.

--- END ISSUE ---

Below are some code segments, each from a relevant file. One or more of these files may contain bugs.
--- BEGIN FILES ---
Path: `evap/evaluation/migrations/0062_replace_textanswer_id_with_uuid.py`
Content:
```
1 # Generated by Django 1.11.3 on 2017-07-03 18:31
2 
3 from django.db import migrations, models
4 import uuid
5 
6 
7 def fill_textanswer_uuid(apps, schema_editor):
8     db_alias = schema_editor.connection.alias
9     TextAnswer = apps.get_model('evaluation', 'TextAnswer')
10     for obj in TextAnswer.objects.using(db_alias).all():
11         obj.uuid = uuid.uuid4()
12         obj.save()
13 
14 
15 class Migration(migrations.Migration):
16 
17     dependencies = [
18         ('evaluation', '0061_editor_review_reminder_template'),
19     ]
20 
21     # Based on
22     # https://gist.github.com/smcoll/8bb867dc631433c01fd0
23 
24     operations = [
25         migrations.AddField(
26             model_name='textanswer',
27             name='uuid',
28             field=models.UUIDField(null=True),
29         ),
30         migrations.RunPython(fill_textanswer_uuid, migrations.RunPython.noop),
31         migrations.AlterField(
32             model_name='textanswer',
33             name='uuid',
34             field=models.UUIDField(primary_key=False, default=uuid.uuid4, serialize=False, editable=False),
35         ),
36         # rename the old id field before deleting it at the end of the
37         # migration for compatibility with the sqlite driver
38         migrations.RenameField(
39             model_name='textanswer',
40             old_name='id',
41             new_name='old_id'
42         ),
43         migrations.RenameField(
44             model_name='textanswer',
45             old_name='uuid',
46             new_name='id'
47         ),
48         migrations.AlterField(
49             model_name='textanswer',
50             name='id',
51             field=models.UUIDField(primary_key=True, default=uuid.uuid4, serialize=False, editable=False),
52         ),
53         migrations.AlterModelOptions(
54             name='textanswer',
55             options={'ordering': ['id'], 'verbose_name': 'text answer', 'verbose_name_plural': 'text answers'},
56         ),
57         migrations.RemoveField(model_name='textanswer', name='old_id'),
58     ]
59
```
--- END FILES ---

Please first localize the bug based on the issue statement, and then generate a patch according to the `git diff` format fenced by three backticks.

Here is an example:

```diff
diff --git a/examples/server_async.py b/examples/server_async.py
--- a/examples/server_async.py
+++ b/examples/server_async.py
@@ -313,4 +313,4 @@
 
 
 if __name__ == "__main__":
-    asyncio.run(run_async_server("."), debug=True)
+    asyncio.run(run_async_server(), debug=True)
diff --git a/examples/server_sync.py b/examples/server_sync.py
--- a/examples/server_sync.py
+++ b/examples/server_sync.py
@@ -313,5 +313,5 @@
 
 
 if __name__ == "__main__":
-    server = run_sync_server(".")
+    server = run_sync_server()
     server.shutdown()

```

diff --git a/evap/evaluation/migrations/0062_replace_textanswer_id_with_uuid.py b/evap/evaluation/migrations/0062_replace_textanswer_id_with_uuid.py
--- a/evap/evaluation/migrations/0062_replace_textanswer_id_with_uuid.py
+++ b/evap/evaluation/migrations/0062_replace_textanswer_id_with_uuid.py
@@ -33,13 +33,12 @@
             name='uuid',
             field=models.UUIDField(primary_key=False, default=uuid.uuid4, serialize=False, editable=False),
         ),
-        # rename the old id field before deleting it at the end of the
-        # migration for compatibility with the sqlite driver
-        migrations.RenameField(
-            model_name='textanswer',
-            old_name='id',
-            new_name='old_id'
-        ),
+        # this causes trouble with sqlite. We have two open bug reports with django for this, see
+        # https://code.djangoproject.com/ticket/29790 and https://code.djangoproject.com/ticket/28541
+        # We can not get this to work with sqlite and postgres right now and we want django2.1, we only
+        # support postgres here. For sqlite, you need to rename the field here and move the RemoveField to
+        # the end.
+        migrations.RemoveField(model_name='textanswer', name='id'),
         migrations.RenameField(
             model_name='textanswer',
             old_name='uuid',
@@ -54,5 +53,4 @@
             name='textanswer',
             options={'ordering': ['id'], 'verbose_name': 'text answer', 'verbose_name_plural': 'text answers'},
         ),
-        migrations.RemoveField(model_name='textanswer', name='old_id'),
     ]

{"golden_diff": "diff --git a/evap/evaluation/migrations/0062_replace_textanswer_id_with_uuid.py b/evap/evaluation/migrations/0062_replace_textanswer_id_with_uuid.py\n--- a/evap/evaluation/migrations/0062_replace_textanswer_id_with_uuid.py\n+++ b/evap/evaluation/migrations/0062_replace_textanswer_id_with_uuid.py\n@@ -33,13 +33,12 @@\n             name='uuid',\n             field=models.UUIDField(primary_key=False, default=uuid.uuid4, serialize=False, editable=False),\n         ),\n-        # rename the old id field before deleting it at the end of the\n-        # migration for compatibility with the sqlite driver\n-        migrations.RenameField(\n-            model_name='textanswer',\n-            old_name='id',\n-            new_name='old_id'\n-        ),\n+        # this causes trouble with sqlite. We have two open bug reports with django for this, see\n+        # https://code.djangoproject.com/ticket/29790 and https://code.djangoproject.com/ticket/28541\n+        # We can not get this to work with sqlite and postgres right now and we want django2.1, we only\n+        # support postgres here. For sqlite, you need to rename the field here and move the RemoveField to\n+        # the end.\n+        migrations.RemoveField(model_name='textanswer', name='id'),\n         migrations.RenameField(\n             model_name='textanswer',\n             old_name='uuid',\n@@ -54,5 +53,4 @@\n             name='textanswer',\n             options={'ordering': ['id'], 'verbose_name': 'text answer', 'verbose_name_plural': 'text answers'},\n         ),\n-        migrations.RemoveField(model_name='textanswer', name='old_id'),\n     ]\n", "issue": "Django 2.1 upgrade\nhttps://docs.djangoproject.com/en/2.1/releases/2.1/\r\n\r\nThere is a guide for upgrading: https://docs.djangoproject.com/en/2.1/howto/upgrade-version/\r\n\r\nBasically\r\n* Read the release notes\r\n* update dependencies\r\n* run tests with `python -Wa` and solve deprecation warnings\r\n* put the new django into the requirements\r\n* run tests, fix failures if any\r\n* run tests with `python -Wa` and solve deprecation warnings again\r\n* if there was any new feature in the release notes that might help us, use it\r\n\r\nalso, we need to check the installed python version on production, django 2.1 supports python 3.5 and newer.\n", "before_files": [{"content": "# Generated by Django 1.11.3 on 2017-07-03 18:31\n\nfrom django.db import migrations, models\nimport uuid\n\n\ndef fill_textanswer_uuid(apps, schema_editor):\n    db_alias = schema_editor.connection.alias\n    TextAnswer = apps.get_model('evaluation', 'TextAnswer')\n    for obj in TextAnswer.objects.using(db_alias).all():\n        obj.uuid = uuid.uuid4()\n        obj.save()\n\n\nclass Migration(migrations.Migration):\n\n    dependencies = [\n        ('evaluation', '0061_editor_review_reminder_template'),\n    ]\n\n    # Based on\n    # https://gist.github.com/smcoll/8bb867dc631433c01fd0\n\n    operations = [\n        migrations.AddField(\n            model_name='textanswer',\n            name='uuid',\n            field=models.UUIDField(null=True),\n        ),\n        migrations.RunPython(fill_textanswer_uuid, migrations.RunPython.noop),\n        migrations.AlterField(\n            model_name='textanswer',\n            name='uuid',\n            field=models.UUIDField(primary_key=False, default=uuid.uuid4, serialize=False, editable=False),\n        ),\n        # rename the old id field before deleting it at the end of the\n        # migration for compatibility with the sqlite driver\n        migrations.RenameField(\n            model_name='textanswer',\n            old_name='id',\n            new_name='old_id'\n        ),\n        migrations.RenameField(\n            model_name='textanswer',\n            old_name='uuid',\n            new_name='id'\n        ),\n        migrations.AlterField(\n            model_name='textanswer',\n            name='id',\n            field=models.UUIDField(primary_key=True, default=uuid.uuid4, serialize=False, editable=False),\n        ),\n        migrations.AlterModelOptions(\n            name='textanswer',\n            options={'ordering': ['id'], 'verbose_name': 'text answer', 'verbose_name_plural': 'text answers'},\n        ),\n        migrations.RemoveField(model_name='textanswer', name='old_id'),\n    ]\n", "path": "evap/evaluation/migrations/0062_replace_textanswer_id_with_uuid.py"}], "after_files": [{"content": "# Generated by Django 1.11.3 on 2017-07-03 18:31\n\nfrom django.db import migrations, models\nimport uuid\n\n\ndef fill_textanswer_uuid(apps, schema_editor):\n    db_alias = schema_editor.connection.alias\n    TextAnswer = apps.get_model('evaluation', 'TextAnswer')\n    for obj in TextAnswer.objects.using(db_alias).all():\n        obj.uuid = uuid.uuid4()\n        obj.save()\n\n\nclass Migration(migrations.Migration):\n\n    dependencies = [\n        ('evaluation', '0061_editor_review_reminder_template'),\n    ]\n\n    # Based on\n    # https://gist.github.com/smcoll/8bb867dc631433c01fd0\n\n    operations = [\n        migrations.AddField(\n            model_name='textanswer',\n            name='uuid',\n            field=models.UUIDField(null=True),\n        ),\n        migrations.RunPython(fill_textanswer_uuid, migrations.RunPython.noop),\n        migrations.AlterField(\n            model_name='textanswer',\n            name='uuid',\n            field=models.UUIDField(primary_key=False, default=uuid.uuid4, serialize=False, editable=False),\n        ),\n        # this causes trouble with sqlite. We have two open bug reports with django for this, see\n        # https://code.djangoproject.com/ticket/29790 and https://code.djangoproject.com/ticket/28541\n        # We can not get this to work with sqlite and postgres right now and we want django2.1, we only\n        # support postgres here. For sqlite, you need to rename the field here and move the RemoveField to\n        # the end.\n        migrations.RemoveField(model_name='textanswer', name='id'),\n        migrations.RenameField(\n            model_name='textanswer',\n            old_name='uuid',\n            new_name='id'\n        ),\n        migrations.AlterField(\n            model_name='textanswer',\n            name='id',\n            field=models.UUIDField(primary_key=True, default=uuid.uuid4, serialize=False, editable=False),\n        ),\n        migrations.AlterModelOptions(\n            name='textanswer',\n            options={'ordering': ['id'], 'verbose_name': 'text answer', 'verbose_name_plural': 'text answers'},\n        ),\n    ]\n", "path": "evap/evaluation/migrations/0062_replace_textanswer_id_with_uuid.py"}]}