ImportError with Python modules in Travis CI - linux

Question

I have a set of scripts in .travis.yml which runs perfectly fine at the moment
...
install:
- scripts/travis/install_deps.sh
- virtualenv -p /opt/pyenv/versions/3.6/bin/python3.6 venv
- source venv/bin/activate
- pip install -r requirements.txt
before_script:
- scripts/test.sh
script:
- scripts/travis/build.sh
after_success:
- deactivate
- virtualenv -p /opt/pyenv/versions/2.7/bin/python2.7 venv
- source venv/bin/activate
- pip install -r requirements.txt
...
However, I would like to clean it up a bit so there's less repetition such that .travis.yml looks like
...
install:
- scripts/travis/install_deps.sh
- export PYTHON_VERSION=3.6
- scripts/travis/install_python_deps.sh
before_script:
- scripts/test.sh
script:
- scripts/travis/build.sh
after_success:
- export PYTHON_VERSION=2.7
- scripts/travis/install_python_deps.sh
...
where install_python_deps.sh looks like
#!/usr/bin/env bash
set -e
if [ ! -z "$VIRTUAL_ENV" ]; then deactivate; fi
virtualenv -p "/opt/pyenv/versions/${PYTHON_VERSION}/bin/python${PYTHON_VERSION}" venv
source venv/bin/activate
pip install -r requirements.txt
The problem arises when this is run in travis. The build breaks when test.sh, which runs a python script that relies on a module declared in requirements.txt is not found. Any pointers as to why this is occurring would be greatly appreciated.

Answer 1

The source venv/bin/activate inside scripts/travis/install_python_deps.sh only has effect until the script install_python_deps.sh exits.
If you want to use the installed modules outside the install_python_deps.sh script,
you need to run source venv/bin/activate (again) outside the script too, for example:
...
install:
- scripts/travis/install_deps.sh
- scripts/travis/install_python_deps.sh 3.6
- source venv/bin/activate
before_script:
- scripts/test.sh
script:
- scripts/travis/build.sh
after_success:
- scripts/travis/install_python_deps.sh 2.7
- source venv/bin/activate
...
Note that to make it shorter, I replaced the PYTHON_VERSION environment variable with a command line parameter. You could adjust the scripts/travis/install_python_deps.sh script accordingly:
#!/usr/bin/env bash
set -euo pipefail
PYTHON_VERSION=$1
if [ "$VIRTUAL_ENV" ]; then deactivate; fi
virtualenv -p "/opt/pyenv/versions/${PYTHON_VERSION}/bin/python${PYTHON_VERSION}" venv
source venv/bin/activate
pip install -r requirements.txt