Thanks @adamchainz I searched for libmemcached on Django Trac to ensure no one else is already working or has worked in the past and found this comment by Tim Graham:
I’m not a mac OS user so I can’t say for sure what the issue is here. What does “it always show problems in installing pylibmc and libmemcached” mean? My guess is that the equivalent of
libmemcached-dev(Debian package) isn’t installed. (related StackOverflow). I think it’s not Django’s job to document the requirements of third-party packages. I’d rather enhance pylibmc’s install instructions if needed.
This was then again raised in May 2018 where Tim again mentioned that we won’t be documenting this as a dependency.
The issue has been raised before and the consensus is that it’s not Django’s job to document all the possibilities for various operating systems.
Now 2 years after that, I (and seems some others too) observed it again and we discussed through this forum.
I think given the recurrence of this issue (several times over half a decade), we should rethink our stance and call out them at least in the Troubleshooting section of the contributing guide. This only reduces the hurdle for new contributors.
In the spirit of this, I have created a patch here Doc'd troubleshooting steps for failures when test requirements by ProProgrammer · Pull Request #12660 · django/django · GitHub