Errors setting up buildbot_travis

[stefanseefeld]

I'm setting up a buildbot_travis instance to explore various features. I'm following the process outlined in https://github.com/buildbot/buildbot_travis/blob/master/README.rst, i.e. setting up a virtualenv using Python3, then starting the master.
From within the web interface I spawn a "LocalWorker", then set up https://github.com/buildbot/buildbot.git as "git+poller" project. Doing a "force build" eventually results in lots of build failures with errors in the " setup virtualenv" step, specifically

Setting up virtualenv sandbox
The path python3.5 (from --python=python3.5) does not exist
program finished with exit code 1

I see similar failures for python3.7. Only python3.6 and python2.7 succeed.

[stefanseefeld]

twistd.log
cfg.yml

(I had to rename the cfg.yml file as github prevents me from uploading files with the .yml extension.)

[levitte]

I usually use the full path, i.e. --python=/usr/bin/python3.5