On (at least) Amazon Linux, the virtualenv tool configures python with the following sys.path directories:
'''${PYTHON_ENV}/local/lib64/python2.7/site-packages''${PYTHON_ENV}/local/lib/python2.7/site-packages''${PYTHON_ENV}/lib64/python2.7''${PYTHON_ENV}/lib/python2.7''${PYTHON_ENV}/lib64/python2.7/site-packages''${PYTHON_ENV}/lib/python2.7/site-packages''${PYTHON_ENV}/lib64/python2.7/lib-dynload''${PYTHON_ENV}/local/lib/python2.7/dist-packages''${PYTHON_ENV}/local/lib/python2.7/dist-packages''${PYTHON_ENV}/lib/python2.7/dist-packages''/usr/lib64/python2.7''/usr/lib/python2.7'
However, running pip install PyYAML in that same virtualenv will install the yaml module into the ${PYTHON_ENV}/lib64/python2.7/dist-packages directory, which is not on the search path.
For now, I am working around the problem by creating dist-packages.pth files as follows:
find ${PYTHON_ENV} -type d -name dist-packages -exec sh -c "echo dist-packages > {}.pth" ';'
I have created a pull-request and issue.
I will also be filing a bug-report against virtualenv as soon as I create a self-contained script illustrating the problem.
