net-mgmt/py-napalm: Update to 2.5.0

• Add a patch that fixes the unittests with net-mgmt/py-junos-eznc >= 2.3.0

• Switch to GitHub for a while to make use of the test-suite that isn't available in the sdist, yet.

• Add "do-test" target to make future QA easier.

Changelog:

Note: This is the last release supporting Python 2. Going forward, only

Python 3.6+ will be supported.

https://github.com/napalm-automation/napalm/releases/tag/2.5.0

MFH: 2019Q4