DUNE_PYTHON_ALLOW_GET_PIP

The Dune build system will try to build a virtualenv with pip installed into it, but this can fail in some situations, in particular on Debian and Ubuntu distributions. In this case, you will se a warning message in the CMake output. If you are on Debian or Ubuntu, try installing the python3-venv (for Python 3) and / or python-virtualenv packages, delete your build directory and try configuring again.

If that still does not help, set this variable to allow the Dune build system to download get-pip.py from https://bootstrap.pypa.io/get-pip.py at configure time and execute it to install pip into the freshly set up virtual environment. While this should normally not be necessary anymore, see https://bugs.launchpad.net/debian/+source/python3.4/+bug/1290847 for more information about the underlying distribution bug.