SIFT goes from cv::xfeatures2d to plain cv:: on 3.4.16
Updating to Opencv 3.4.16 and later will remove the dependency of SIFT on xfeatures2d.
This is because the patent of SIFT has expired, and now the algorithm is freely available in the main cv library.
vision_utils should move to opencv 3.4.16 or later. Possibly straight to 4.0.
This will remove the need for !5
Edited by Joan Solà Ortega