Fixed deepcopy for opentime.TimeRange

[reinecke]

The bindings for __deepcopy__ on TimeRange previously didn't accept the memo arg. This was causing the following error:

>>> copy.deepcopy(otio.opentime.TimeRange())
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/Users/ereinecke/.newt-cache/pyenv/versions/3.8.2/lib/python3.8/copy.py", line 153, in deepcopy
    y = copier(memo)
TypeError: __deepcopy__(): incompatible function arguments. The following argument types are supported:
    1. (self: opentimelineio._opentime.TimeRange) -> opentimelineio._opentime.TimeRange

Invoked with: otio.opentime.TimeRange(start_time=otio.opentime.RationalTime(value=0, rate=1), duration=otio.opentime.RationalTime(value=0, rate=1)), {}

I've also added unitests for copy and deepcopy on RationalTime and TimeRange to protect against regression.

[codecov-io]

Codecov Report

Merging #692 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #692   +/-   ##
=======================================
  Coverage   81.72%   81.72%           
=======================================
  Files          72       72           
  Lines        2731     2731           
=======================================
  Hits         2232     2232           
  Misses        499      499           

Flag	Coverage Δ
#py27	81.70% <ø> (ø)
#py36	81.70% <ø> (ø)
#py37	81.70% <ø> (ø)

Impacted Files	Coverage Δ
...imelineio/opentime-bindings/opentime_timeRange.cpp	100.00% <ø> (ø)

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[meshula]

I'm surprised this slipped through the cracks; of course it's not an obvious implementation detail. Did you scan for other deepcopy usages for the same problem?

[reinecke]

I did a quick grep and the others seemed to be alright. I only ran into this because I was using a TimeRange in a dataclass and certain actions in that context trigger a deepcopy. Since RationalTime and TimeRange are effectively immutable there's no real reason for people to be doing this directly.