[swig] fix doxy2swig (was failing on macos with python3).
[swig] fix doxy2swig (was failing on macos with python3).

fperignon/siconos,fperignon/siconos,fperignon/siconos,radarsat1/siconos,siconos/siconos,siconos/siconos,radarsat1/siconos,radarsat1/siconos,fperignon/siconos,radarsat1/siconos,siconos/siconos,fperignon/siconos,radarsat1/siconos,siconos/siconos