It seems the issue is our use of pyenv global to set the python version.
You can read more details in the github issue, but to workaround this, you need to delete .pyenv-version file manually before CircleCI changes python version like this.
machine:
pre:
- rm .python-version
python:
version: 3.5.1
Here is a working build: https://circleci.com/gh/kimh/trusty-test/329
There are a few options to fix this permanently and I need to think a bit to decide which path we want to go. Please use the workaround until we fix the issue.
Thank you for your patience.