BUG: installer.sh erased other PYTHONPATH directories when exporting scripts to python paths
BUG: installer.sh erased other PYTHONPATH directories when exporting scripts to python paths

Former-commit-id: 406ce9064e10dfba3a8fad3194a911bf80152970
Former-commit-id: d701c3ac1a8edc6152b896cadaf2aba3ef907991
3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox