Use backports.functools_lru_cache instead of functools32

[felixonmars]

It's better maintained and more widely used (by pylint, jaraco, etc).

[tacaswell]

I am mixed on this. A bit worried that changing the deps is going to just cause havoc for down-stream packagers as this is a new for 2.0 dependency, but sympathetic to using a more widely used / better maintained backport.

[felixonmars]

I guess the havoc would be limited, since most distros have pylint packaged, they will have backports.functools_lru_cache already :)

[anntzer]

Apparently pylint only started depending on backports.functools_lru_cache recently (PyCQA/pylint@02f6823). For example, a quick search on pkgs.org suggests that none of CentOS, Debian Jessie, Mageia and Ubuntu (in their latest versions) provide that package right now.

[HolgerPeters]

Not a linux distributor, but I bundle packages nonetheless and https://pypi.python.org/pypi/backports.functools_lru_cache seems to be a more mature package on a quick glance.

[NelleV]

I am fine either way. @tacaswell I think you should be the one making the decision on this change, as you are the maintainer 😈

[tacaswell]

I am 👍 on this for 2.1. Can you also put a file in https://github.com/matplotlib/matplotlib/tree/master/doc/api/api_changes with basically the first message from this PR?

[tacaswell]

modulo and api_changes entry.

[felixonmars]

API changes file added :)

[felixonmars]

Hrm, the test failure looks irrelevant.

[NelleV]

Thanks @felixonmars !