security/py-ecdsa: Update to 0.16.0

[loader]

Summary

Proposed commit log message:

security/py-ecdsa: Update to 0.16.0

- Update to 0.16.0
- Add test target
- Pet portlint

Changelog:

    https://github.com/warner/python-ecdsa/releases/tag/python-ecdsa-0.16.0

Reviewed_by: koobs
Approved by: koobs (ports, mentor, maintainer)
Differential_Revision: D27187
MFH: No (API changes, unclear on compatibility)

Test Plan

• portlint: OK (looks fine.)
• testport: OK (poudriere: 1300123, [amd64], 'BUILD_ALL_PYTHON_FLAVORS=1', [py27, py36, py37, py38, py39] tested)
• unittest: OK (

Python3.6 on amd64: 1473 passed in 209.06 seconds
Python3.7 on amd64: 1346 passed in 119.79 seconds
Python3.8 on amd64: 1418 passed in 144.18 seconds
Python3.9 on amd64: 1418 passed in 141.26 seconds
)

[koobs]

Perfect :)

[loader]

Thanks, @koobs.