Python subprocess can't work more

[native-api]

Xenial as the default build environment - Travis CI changelog

In particular, in the raw log, I see an error about pip inable to upgrade some (presumably apt-installed) Python packages which ultimately results in an error about an incompatible version of one of them being present.

Python 3.6 and 3.7 with system_site_packages enabled fails to activate on xenial

You don’t. "System site-packages" is only a thing for Python versions provided by distro – which for Xenial are 2.7.12 and 3.5.1. Other Python versions are installed manually (into /opt as of this writing), and the only global packages there are pip and setuptools (you can see all this by examining the Python tarball that the build log refers to). So if you’re using alternative Python versions, you don’t have access to any apt-get Python packages anyway. As such, the most straightforward solu…