Django Prometheus Error

.log

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "/usr/bin/py.test", line 11, in <module>
    sys.exit(main())
  File "/usr/lib/python3.5/site-packages/_pytest/config.py", line 50, in main
    config = _prepareconfig(args, plugins)
  File "/usr/lib/python3.5/site-packages/_pytest/config.py", line 160, in _prepareconfig
    pluginmanager=pluginmanager, args=args)
  File "/usr/lib/python3.5/site-packages/pluggy/__init__.py", line 617, in __call__
    return self._hookexec(self, self._nonwrappers + self._wrappers, kwargs)
  File "/usr/lib/python3.5/site-packages/pluggy/__init__.py", line 222, in _hookexec
    return self._inner_hookexec(hook, methods, kwargs)
  File "/usr/lib/python3.5/site-packages/pluggy/__init__.py", line 216, in <lambda>
    firstresult=hook.spec_opts.get('firstresult'),
  File "/usr/lib/python3.5/site-packages/pluggy/callers.py", line 196, in _multicall
    gen.send(outcome)
  File "/usr/lib/python3.5/site-packages/_pytest/helpconfig.py", line 68, in pytest_cmdline_parse
    config = outcome.get_result()
  File "/usr/lib/python3.5/site-packages/pluggy/callers.py", line 76, in get_result
    raise ex[1].with_traceback(ex[2])
  File "/usr/lib/python3.5/site-packages/pluggy/callers.py", line 180, in _multicall
    res = hook_impl.function(*args)
  File "/usr/lib/python3.5/site-packages/_pytest/config.py", line 943, in pytest_cmdline_parse
    self.parse(args)
  File "/usr/lib/python3.5/site-packages/_pytest/config.py", line 1108, in parse
    self._preparse(args, addopts=addopts)
  File "/usr/lib/python3.5/site-packages/_pytest/config.py", line 1079, in _preparse
    args=args, parser=self._parser)
  File "/usr/lib/python3.5/site-packages/pluggy/__init__.py", line 617, in __call__
    return self._hookexec(self, self._nonwrappers + self._wrappers, kwargs)
  File "/usr/lib/python3.5/site-packages/pluggy/__init__.py", line 222, in _hookexec
    return self._inner_hookexec(hook, methods, kwargs)
  File "/usr/lib/python3.5/site-packages/pluggy/__init__.py", line 216, in <lambda>
    firstresult=hook.spec_opts.get('firstresult'),
  File "/usr/lib/python3.5/site-packages/pluggy/callers.py", line 201, in _multicall
    return outcome.get_result()
  File "/usr/lib/python3.5/site-packages/pluggy/callers.py", line 76, in get_result
    raise ex[1].with_traceback(ex[2])
  File "/usr/lib/python3.5/site-packages/pluggy/callers.py", line 180, in _multicall
    res = hook_impl.function(*args)
  File "/usr/lib/python3.5/site-packages/pytest_django/plugin.py", line 246, in pytest_load_initial_conftests
    _setup_django()
  File "/usr/lib/python3.5/site-packages/pytest_django/plugin.py", line 149, in _setup_django
    django.setup()
  File "/usr/lib/python3.5/site-packages/django/__init__.py", line 24, in setup
    apps.populate(settings.INSTALLED_APPS)
  File "/usr/lib/python3.5/site-packages/django/apps/registry.py", line 120, in populate
    app_config.ready()
  File "/usr/lib/python3.5/site-packages/django_prometheus/apps.py", line 24, in ready
    ExportMigrations()
  File "/usr/lib/python3.5/site-packages/django_prometheus/migrations.py", line 46, in ExportMigrations
    executor = MigrationExecutor(connections[alias])
  File "/usr/lib/python3.5/site-packages/django/db/migrations/executor.py", line 18, in __init__
    self.loader = MigrationLoader(self.connection)
  File "/usr/lib/python3.5/site-packages/django/db/migrations/loader.py", line 49, in __init__
    self.build_graph()
  File "/usr/lib/python3.5/site-packages/django/db/migrations/loader.py", line 206, in build_graph
    self.applied_migrations = recorder.applied_migrations()
  File "/usr/lib/python3.5/site-packages/django/db/migrations/recorder.py", line 61, in applied_migrations
    if self.has_table():
  File "/usr/lib/python3.5/site-packages/django/db/migrations/recorder.py", line 44, in has_table
    return self.Migration._meta.db_table in self.connection.introspection.table_names(self.connection.cursor())
  File "/usr/lib/python3.5/site-packages/django/db/backends/base/base.py", line 255, in cursor
    return self._cursor()
  File "/usr/lib/python3.5/site-packages/django/db/backends/base/base.py", line 232, in _cursor
    self.ensure_connection()
  File "/usr/lib/python3.5/site-packages/django/db/backends/base/base.py", line 216, in ensure_connection
    self.connect()
  File "/usr/lib/python3.5/site-packages/django/db/utils.py", line 89, in __exit__
    raise dj_exc_value.with_traceback(traceback) from exc_value
  File "/usr/lib/python3.5/site-packages/django/db/backends/base/base.py", line 216, in ensure_connection
    self.connect()
  File "/usr/lib/python3.5/site-packages/django/db/backends/base/base.py", line 194, in connect
    self.connection = self.get_new_connection(conn_params)
  File "/usr/lib/python3.5/site-packages/django_prometheus/db/common.py", line 41, in get_new_connection
    *args, **kwargs)
  File "/usr/lib/python3.5/site-packages/django/db/backends/mysql/base.py", line 236, in get_new_connection
    return Database.connect(**conn_params)
  File "/usr/lib/python3.5/site-packages/MySQLdb/__init__.py", line 86, in Connect
    return Connection(*args, **kwargs)
  File "/usr/lib/python3.5/site-packages/MySQLdb/connections.py", line 204, in __init__
    super(Connection, self).__init__(*args, **kwargs2)
django.db.utils.OperationalError: (2005, "Unknown MySQL server host 'db' (-2)")