dune-py does not rebuild after update of system dune-python
Updating an installed version of dune-python (or dependent modules, like dune-alugrid) does not force dune-py to rebuild already compiled python modules.
The problem seems to originate from CMake. Updating any system headers or system libraries does not cause CMake to recompile dependent source code in user projects. This behavior might be ok for normal projects built via CMake. However, we should avoid forcing users of dune-python to remove their dune-py module, although we might want to suggest this action upon upgrading installed dune modules anyway.
While we have a mechanism in dune-python to force completely rebuilding dune-py, this mechanism is currently restricted to changes in dune-python and designed for changes in the builder infrastructure. Due to this surprising behavior of CMake, it might be insufficient, though.