SAGE_SPKG_CONFIGURE(
    [threejs], [dnl direct testing of file existence
      AC_MSG_CHECKING(ThreeJS installation...)
      if [[ -f %%LOCALBASE%%/www/threejs/Three.js ]] ; then
        AC_MSG_RESULT(OK)
      else
        AC_MSG_RESULT(KO)
        sage_spkg_install_threejs=yes
      fi
])