When MITK_USE_SYSTEM_PYTHON is switched on, currently an error occures.

Apparently it can be fixed by adding:

PYTHONUSERBASE=${_install_dir} to

COMMAND  PYTHONUSERBASE=${_install_dir} ${PYTHON_EXECUTABLE} setup.py install --prefix=${_install_dir}

in SimpleItk.cmake. However, this needs to be conditional on whether or not MITK_USE_SYSTEM_PYTHON is switched on.