install: try to add pip requirements for py3k
install: try to add pip requirements for py3k

Former-commit-id: 0f83c9046cdc2661243752a9538c7b0e0c56b04b
neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox