py-u-msgpack-python: new port

[herbygillot]

Tested on

macOS 10.15.6 19G73
Xcode 11.6 11E708

Verification

Have you

• followed our Commit Message Guidelines?
• squashed and minimized your commits?
• checked that there aren't other open pull requests for the same change?
• referenced existing tickets on Trac with full URL?

• checked your Portfile with port lint?
• tried existing tests with sudo port test?
• tried a full install with sudo port -d install?
• tested basic functionality of all binary files?

[macportsbot]

Travis Build #13349 Passed.

Lint results

--->  Verifying Portfile for py-u-msgpack-python
--->  0 errors and 0 warnings found.

Port py38-u-msgpack-python success on xcode10.3. Log
Port py-u-msgpack-python success on xcode10.3. Log
Port py38-u-msgpack-python success on xcode9.4. Log
Port py-u-msgpack-python success on xcode9.4. Log
Port py38-u-msgpack-python success on xcode8.3. Log
Port py-u-msgpack-python success on xcode8.3. Log
Port py38-u-msgpack-python success on xcode7.3. Log
Port py-u-msgpack-python success on xcode7.3. Log