cache.get and cache.set should have consistent key rules across different backends

[rbanffy]

As it is now, cache.get and cache.set accept keys with spaces when CACHE_BACKEND is set to 'locmem://', but memcached complains of keys with spaces. This makes tests work on a non-memcached setup (i.e. development workstation) and fail on the server (using memcached)

[Carl Meyer]

I've also been bitten by this.

[James Bennett]

This isn't anywhere near important enough to be on the 1.2 milestone, and given the history of proposals related to this (see #6447 and #3241 in particular), probably needs a decision from the committers before being accepted.

[Carl Meyer]

Fair enough re 1.2 milestone.

This is actually probably a duplicate of #6447, though this ticket more clearly requests what I think is the right solution; that the caching system should enforce the most-stringent key rules of any cache backend so code with bad keys fails fast rather than in production only. Seems like this is the unavoidable solution if cache backends are really intended to be interchangeable, and for caching to be usable by reusable code. AFAICS that solution was never proposed or rejected in any of the previous related tickets.

[Carl Meyer]

Marking duplicate of #6447.