Travis-CI python3.6 Tox launching virtualenv error

[Wei-1]

We are using tox for py36 test environment setup through travis-ci, the tests start breaking in 2021-10-23.

The error that we are getting is:

$ tox
GLOB sdist-make: /home/travis/build/apache/incubator-marvin/python-toolbox/setup.py
py36 create: /home/travis/build/apache/incubator-marvin/python-toolbox/.tox/py36
ERROR: invocation failed (exit code 1), logfile: /home/travis/build/apache/incubator-marvin/python-toolbox/.tox/py36/log/py36-0.log
================================== log start ===================================
StopIteration: 
=================================== log end ====================================
ERROR: InvocationError for command /home/travis/virtualenv/python3.6.7/bin/python -m virtualenv --no-download --python /home/travis/virtualenv/python3.6.7/bin/python py36 (exited with code 1)
___________________________________ summary ____________________________________
ERROR:   py36: InvocationError for command /home/travis/virtualenv/python3.6.7/bin/python -m virtualenv --no-download --python /home/travis/virtualenv/python3.6.7/bin/python py36 (exited with code 1)
The command "tox" exited with 1.

Full Log Travis-CI Link

The log showed that the process had failed while launching virtualenv even before package installation.

We had also tested with tox -rvve py36 for more logs:

Another log with Travis-CI Link

The test result showed that /home/travis/virtualenv/python3.6.7/bin/python does exist, and can be successfully executed.

What is weird to us is that the same setting used to be able to run without failure in 2021-10-22:

Previous log with Travis-CI Link

And the only difference seem to be the version change of virtualenv, which is changing from 20.8.1 to 20.9.0 or 20.10.0.

Does anyone know how this can be fixed?

[gaborbernat]

Can you please amend your travis file to show the tox run in verbose mode? tox -vvv that is.

[Wei-1]

After adding the verbose, I actually don't see much different in the log though.
https://app.travis-ci.com/github/apache/incubator-marvin/jobs/550859698

[gaborbernat]

You could try to invoke the failing command directly and see what gives:

/home/travis/virtualenv/python3.6.7/bin/python -m virtualenv --no-download --python /home/travis/virtualenv/python3.6.7/bin/python py36

(add -vvv for that verbose mode too). Also please check the virtualenv version. Based on this I can conclude that 99% of this is a broken virtualenv/python distribution on Travis, and is not otherwise related to tox.

[Wei-1]

There are several dependencies that could be the cause of the issue.
apache/incubator-marvin#59
In our test, we ended up change the Ubuntu version for the right OpenSSL dependency.