Segmentation fault: 11 error ( OpenCV )
Maybe duplicate of https://stackoverflow.com/questions/28669587/python-segmentation-fault-11-when-running-import-cv-or-import-cv2. 
Did you install python through brew? If yes then there is probably crash between built-in version that ships with macOS and that installed through brew. Try using absolute path /usr/bin/python -c "import cv2" (built-in) and /usr/local/bin/python -c "import cv" (from brew). One should probably work.