Propagating Python bindings version in system tests (conflict with requirements.txt)

[MakisH]

We now automatically install all dependencies in our Python-based tutorials via a requirements.txt, where we also specify pyprecice.

At the same time, we have an argument to ask for a specific Python bindings version to test.

This argument is now ignored, since we are executing inside a venv.

[BenjaminRodenberg]

For the transition period the option --system-site-packages (see here) offers a possible work around: The tutorial we run will ignore system packages. Docker images that are not updated to installing into a venv will install packages on system level.

Example: https://github.com/precice/fenics-adapter/blob/develop/tools/releasing/packaging/docker/Dockerfile installs the specified version of fenicsprecice on system level. In here we use --system-site-packages. Therefore the partitioned heat conduction tutorial will use the system level fenics-adapter. Ideally, we would install the fenics-adapter to a given venv and let the tutorial use that version. Note that for this specific case we still need --system-site-packages since we can only install FEniCS on system level unfortunately.

[BenjaminRodenberg]

A comment on the "conflict between requirements.txt and the specific version required by a user of the systemtests":

I'm not sure that there is really a conflict: If in the requirements.txt we ask for pyprecice~=3.0 this requirement should be satisfied by any commit based on https://github.com/precice/python-bindings/tree/v3.0.0.0. If the specification in the requirements file triggers overwriting the version of pyprecice that the user of the systemtests originally asked for there are two possibilities:

1. something is wrong with the specification in the requirements.txt; e.g. an overly strict specification that excludes the current develop version.
2. something is wrong with the commit the user of the systemtests provides in the first place; e.g. we want to test some pyprecice@v4 with a tutorial requesting pyprecice~=3.0.