[BUG] memcached support with django 4.1 and above

[lrrb]

Describe the bug

I can't use memcached with Graphite and Django 4.2
Django 4.x+ has removed python-memcached
https://docs.djangoproject.com/en/5.1/releases/4.1/

/opt/graphite# export PYTHONPATH=/opt/graphite/webapp
 (graphite) root@my-server:/opt/graphite# export DJANGO_SETTINGS_MODULE=graphite.settings
 (graphite) root@my-server:/opt/graphite# django-admin migrate
 Traceback (most recent call last):
   File "/opt/graphite/lib/python3.11/site-packages/django/utils/module_loading.py", line 30, in import_string
     return cached_import(module_path, class_name)
            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   File "/opt/graphite/lib/python3.11/site-packages/django/utils/module_loading.py", line 16, in cached_import
     return getattr(module, class_name)
            ^^^^^^^^^^^^^^^^^^^^^^^^^^^
 AttributeError: module 'django.core.cache.backends.memcached' has no attribute 'MemcachedCache'. Did you mean: 'PyMemcacheCache'?

To Reproduce

Enable memcached in local_settings.py

MEMCACHE_HOSTS = ['127.0.0.1:11211']

Expected behavior

I would like to install pymecached and be able to use Graphite with memcached.

Environment (please complete the following information):

• OS flavor: Ubuntu 22
• Graphite-web version: current master
• Django/Python version Django 4.2 python 3.11

[lrrb]

fixed with #2878