Cleanups when no supported version of Django supports Python 2 anymore

[Aymeric Augustin]

Compatibility with Python 2 is currently being removed in master as part of the Django 2.0 development cycle: see #23919.

However third-party apps may want to remain compatible with all supported version of Django and the corresponding versions of Python, which includes Python 2.

To allow this, compatibility functions or modules aren't removed. They're still importable. They're usually just aliases or no-ops. Here's a list of things to deprecate and remove eventually:

• django.utils.six
• django.utils.lru_cache
• django.utils._os.abspathu, upath, npath
• django.utils.decorators.available_attrs
• django.utils.encoding.python_2_unicode_compatible
• django.utils.encoding.smart/force_text
• django.utils.http.urlquote/urlquote_plus/urlunquote/urlunquote_plus (​unmerged commit)

[Simon Charette]

Should we revert the removal of eb0b921c29ace8643a5a4cd136c433727c53dead in this case?

[Tim Graham]

Those methods don't work on Python 3 (AttributeError: 'dict' object has no attribute 'iterkeys') so I don't think they have value for the use case described in the ticket description. A third-party app should use six.iterkeys() as the old test did (which uses keys() etc. on Python 3), or am I missing something?

[Claude Paroz]

The question we discussed on IRC and GitHub with Tim is about deprecating or not deprecating those items.

I would be for a standard deprecation process as I don't see how this is different from any other deprecation. But I'm open to read about use cases which would push for a delayed deprecation process for items related to Python 2.