TEST: fixed straightening test
TEST: fixed straightening test

Former-commit-id: 66f817088c5b38da6d253912e6d2f66754ed7e97
Former-commit-id: 8207c778cede60d96c2f4735dfb0c4f7c52eddfc
3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox