Bump pyzipkin to 0.17.0

[illicitonion]

This supports python 3.7.

[Eric-Arellano]

Great! I think we should include this before your release @stuhood, otherwise ./pants3 won't work for Python 3.7 users.

[stuhood]

Great! I think we should include this before your release @stuhood, otherwise ./pants3 won't work for Python 3.7 users.

I just cut #7170, so this made it in.

But to be clear: pants3 is not exposed to end users: only to the pantsbuild/pants repo. End users generally use https://www.pantsbuild.org/install.html#recommended-installation, and so unless we give them a method of creating a Py3 aware pants script (see the curl in that section), they will continue to use Py2.