Datetime timezone handling.

[JNRowe]

Feeble brainstorming session...

I've just been bitten quite badly by the lack of timezone handling, the cause is the use of naive datetime objects in the 'GitHub' timezone(America/Los_Angeles). While processing some tasks that span the PST/PDT changeover the ordering of events is broken.

Options are:

1. Leave alone and try to process the datetime objects externally, somewhat easy but not a good solution as it requires duplication in each project that requires accurate date handling
2. Start producing non-naive datetime objects, breaks any caller who is not prepared for it.
3. Introduce a setting to toggle naive object availability, defaulting to naive objects to maintain backwards compatibility

python-dateutil makes handling option 1 quite easy, and also simplifies the handling of option 3 at the cost of another external dependency. Option 2 is just pure evil, or pure stupidity depending on point of view.

Option 3 results in a parsing using something like the following entirely untested code:

datetime_ = parser.parse(github_date)
if NAIVE:
    datetime_.replace(tzinfo=None)
return datetime_

And similarly producing GitHub compatible date strings would require handling of naive formats with equally untested code such as:

if NAIVE:
    datetime_ = datetime_.replace(tz.gettz("America/Los_Angeles"))
return datetime_.strftime("%Y/%m/%d %H:%M:%S %z")

[JNRowe]

The lack of timezone handling also exhibits itself for any consumers who use a timedelta to convert to local time for the duration of any gap between GitHub's switch to DST and their own. On the order of 2-4 weeks a year for regions that I personally care about ;)

[JNRowe]

First-run implementation of option 3 from above. Works, but needs some refactoring.

[JNRowe]

With the pull request merge there is a new issue of handling timezones because pull requests don't use the "GitHub timezone".

[JNRowe]

The mostly new commits now listed in this pull request(JNRowe/python-github2 feat/timezone_support) are what I'm planning to merge RSN.