Djangoのcreatesuperuserで「AssertionError: database connection isn't set to UTC」発生

##概要
Django + psycopg2 で posgreSQL に接続しており、createsuperuser を実行すると「AssertionError: database connection isn't set to UTC」が発生し、スーパーユーザーが作成できない。

```
$ python manage.py createsuperuser
Traceback (most recent call last):
  File "manage.py", line 22, in <module>
    main()
  File "manage.py", line 18, in main
    execute_from_command_line(sys.argv)
  File "C:\Python\Python38\lib\site-packages\django\core\management\__init__.py", line 401, in execute_from_command_line
    utility.execute()
  File "C:\Python\Python38\lib\site-packages\django\core\management\__init__.py", line 395, in execute
    self.fetch_command(subcommand).run_from_argv(self.argv)
  File "C:\Python\Python38\lib\site-packages\django\core\management\base.py", line 328, in run_from_argv
    self.execute(*args, **cmd_options)
  File "C:\Python\Python38\lib\site-packages\django\contrib\auth\management\commands\createsuperuser.py", line 79, in execute
    return super().execute(*args, **options)
  File "C:\Python\Python38\lib\site-packages\django\core\management\base.py", line 368, in execute
    self.check_migrations()
  File "C:\Python\Python38\lib\site-packages\django\core\management\base.py", line 458, in check_migrations
    executor = MigrationExecutor(connections[DEFAULT_DB_ALIAS])
  File "C:\Python\Python38\lib\site-packages\django\db\migrations\executor.py", line 18, in __init__
    self.loader = MigrationLoader(self.connection)
  File "C:\Python\Python38\lib\site-packages\django\db\migrations\loader.py", line 49, in __init__
    self.build_graph()
  File "C:\Python\Python38\lib\site-packages\django\db\migrations\loader.py", line 212, in build_graph
    self.applied_migrations = recorder.applied_migrations()
  File "C:\Python\Python38\lib\site-packages\django\db\migrations\recorder.py", line 77, in applied_migrations
    return {(migration.app, migration.name): migration for migration in self.migration_qs}
  File "C:\Python\Python38\lib\site-packages\django\db\models\query.py", line 276, in __iter__
    self._fetch_all()
  File "C:\Python\Python38\lib\site-packages\django\db\models\query.py", line 1261, in _fetch_all
    self._result_cache = list(self._iterable_class(self))
  File "C:\Python\Python38\lib\site-packages\django\db\models\query.py", line 57, in __iter__
    results = compiler.execute_sql(chunked_fetch=self.chunked_fetch, chunk_size=self.chunk_size)
  File "C:\Python\Python38\lib\site-packages\django\db\models\sql\compiler.py", line 1184, in execute_sql
    return list(result)
  File "C:\Python\Python38\lib\site-packages\django\db\models\sql\compiler.py", line 1583, in cursor_iter
    for rows in iter((lambda: cursor.fetchmany(itersize)), sentinel):
  File "C:\Python\Python38\lib\site-packages\django\db\models\sql\compiler.py", line 1583, in <lambda>
    for rows in iter((lambda: cursor.fetchmany(itersize)), sentinel):
  File "C:\Python\Python38\lib\site-packages\django\db\utils.py", line 97, in inner
    return func(*args, **kwargs)
  File "C:\Python\Python38\lib\site-packages\django\db\backends\postgresql\utils.py", line 6, in utc_tzinfo_factory
    raise AssertionError("database connection isn't set to UTC")
AssertionError: database connection isn't set to UTC
```

##結論
psycopg2のバージョンが原因らしい。
現在インストールされているバージョンは2.9.1だった。

```
pip show psycopg2
Name: psycopg2
Version: 2.9.1
Summary: psycopg2 - Python-PostgreSQL Database Adapter
Home-page: https://psycopg.org/
Author: Federico Di Gregorio
Author-email: fog@initd.org
License: LGPL with exceptions
Location: c:\python\python38\lib\site-packages
Requires:
Required-by:
```

psycopg2を一度アンインストールし、バージョン2.8.6を指定して再インストール。

```
$ pip uninstall psycopg2
Found existing installation: psycopg2 2.8.6
Uninstalling psycopg2-2.9.1:
  Would remove:
    c:\python\python38\lib\site-packages\psycopg2-2.9.1.dist-info\*
    c:\python\python38\lib\site-packages\psycopg2\*
Proceed (y/n)? y
  Successfully uninstalled psycopg2-2.9.1

$ pip install psycopg2==2.8.6
WARNING: Value for scheme.headers does not match. Please report this to <https://github.com/pypa/pip/issues/9617>
distutils: c:\python\python38\Include\UNKNOWN
sysconfig: c:\python\python38\Include
WARNING: Additional context:
user = False
home = None
root = None
prefix = None
Collecting psycopg2==2.8.6
  Downloading psycopg2-2.8.6-cp38-cp38-win_amd64.whl (1.1 MB)
     |████████████████████████████████| 1.1 MB 6.4 MB/s
Installing collected packages: psycopg2
WARNING: Value for scheme.headers does not match. Please report this to <https://github.com/pypa/pip/issues/9617>
distutils: c:\python\python38\Include\UNKNOWN
sysconfig: c:\python\python38\Include
WARNING: Additional context:
user = False
home = None
root = None
prefix = None
Successfully installed psycopg2-2.8.6
```

インストールが完了したので、改めて createsuperuser を実行。

```
# python manage.py createsuperuser
ユーザー名 (leave blank to use '******'): admin
メールアドレス:
Password:
Password (again):
Superuser created successfully.
```

無事にスーパーユーザーを作成できました。

##参考
https://exerror.com/assertionerror-database-connection-isnt-set-to-utc/