INST: made input arg mandatory
INST: made input arg mandatory

Former-commit-id: 5e986c8ac3a64d5b6f45199ac802342fa4ec2d22 [formerly fd33d1dffa4ae236cce0cb0192ee4913e4ae1d45]
Former-commit-id: 3e2070092e059262d444008fd1afab57bf9fd4be
Former-commit-id: 24067142948b7ba984a26116726ea3928fcb9eb6
neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox