As the code copied from the nix store, the files there do not have the 'writeable' permission.
Hence this fix, needed on nix but not on usual LSB linuces.
diff --git a/source/creator/CMakeLists.txt b/source/creator/CMakeLists.txt
index 386ef1b..6a180fa 100644
--- a/source/creator/CMakeLists.txt
+++ b/source/creator/CMakeLists.txt
@@ -152,6 +152,7 @@ IF(WITH_INSTALL)
 				COMMAND mkdir ${TARGETDIR}/.blender/python # PYTHONPATH and PYTHONHOME is set here
 				COMMAND mkdir ${TARGETDIR}/.blender/python/lib/
 				COMMAND cp -R ${PYTHON_LIBPATH}/python${PYTHON_VERSION} ${TARGETDIR}/.blender/python/lib/
+        COMMAND chmod -R +w ${TARGETDIR}/.blender/python/lib/
         
 				COMMAND rm -rf ${TARGETDIR}/.blender/python/lib/python${PYTHON_VERSION}/distutils
 				COMMAND rm -rf ${TARGETDIR}/.blender/python/lib/python${PYTHON_VERSION}/lib2to3