Improve timezone support

[chrismd]

We should allow the user to specify the timezone offset explicitly and also to support named timezones through an optional dependency on something like pytz.

[chrismd (chrismd)]

I've added a dependency on pytz to allow support of Olson timezones and fixed the x-label formatting to be based off timezone-aware datetime objects instead of attempting to calculate the offset manually (which was quite error prone).

[Nicholas Leskiw (nleskiw)]

I installed a fresh copy of trunk, and all rendering fails with

ViewDoesNotExist: Could not import graphite.render.views. Error was: No module named pytz

It appears to be required (at least on Ubuntu 10.04)

Anyway, we can either add a fatal warning to check-dependencies.py or add a workaround if you don't want it to be required.
Or am I screwing something up?

[Nicholas Leskiw (nleskiw)]

After a sudo apt-get install python-tz rendering works. I'm guessing it's not optional right now.

[chrismd (chrismd)]

Correct, pytz is a new required dependency for Graphite. I am going to try and bundle it in the upcoming release so a separate installation of pytz isn't needed (but would override the bundled version if present).