Fixed 2 to 3 porting bug in pynche.ColorDB.

Original patch by Akira Li.

 * Eliminated OverflowError from timedelta * float for some floats;
 * Corrected rounding in timedlta true division.

implementation in issue #21408 they are redundant.

This patch brings the pure-python datetime more in-line with the C
module.  Patch contributed by Brian Kearns, a PyPy developer.  PyPy
project has been running these modifications in PyPy2 stdlib.

This commit includes:

- General PEP8/cleanups;
- Better testing of argument types passed to constructors;
- Removal of duplicate operations;
- Optimization of timedelta creation;
- Caching the result of __hash__ like the C accelerator;
- Enhancements/bug fixes in tests.

class name instead of hardcoded one.

error messages and comments.

ModuleNotFoundError.

timezone instance corresponding to the system local timezone when
called with no arguments.

timezone instance corresponding to the system local timezone when
called with no arguments.

or datetime objects.

time.ctime(), gmtime(), time.localtime(), datetime.date.fromtimestamp(),
datetime.datetime.fromtimestamp() and datetime.datetime.utcfromtimestamp() now
raises an OverflowError, instead of a ValueError, if the timestamp does not fit
in time_t.

datetime.datetime.fromtimestamp() and datetime.datetime.utcfromtimestamp() now
round microseconds towards zero instead of rounding to nearest with ties going
away from zero.

Patch by Victor Stinner.