Fix the creation of the ipython notebook wrapper script

python/CMakeLists.txt

 # Install some additional packages into the virtualenv.
-execute_process(COMMAND dune-env python -m pip install ipython ipdb jupyter
-                WORKING_DIRECTORY ${CMAKE_BINARY_DIR})
+#
+# Install path.py in version 7.7 is to avoid a bug in
+# IPythons dependency pickleshare.
+execute_process(COMMAND ${CMAKE_BINARY_DIR}/dune-env-2 python -m pip install path.py==7.7 tornado>=4.0 ipython>=4.0.0 jupyter>=1.0.0)
 
 # Create an ipython notebook wrapper!
-create_virtualenv_wrapper(ENVPATH ${DUNE_PYTHON_VIRTUALENV_PATH}
-                          COMMANDS ipython notebook
+create_virtualenv_wrapper(ENVPATH ${dune-python_DIR}/python2-env
+                          COMMANDS python -m IPython notebook
                           NAME notebook)
 
 # Install all the external packages that we have as submodules