$ cmake -D CMAKE_BUILD_TYPE=RELEASE
    -D CMAKE_INSTALL_PREFIX=/usr/local
    -D OPENCV_EXTRA_MODULES_PATH=~/opencv_contrib/modules
    -D PYTHON3_LIBRARY=YYY
    -D PYTHON3_INCLUDE_DIR=ZZZ
    -D PYTHON3_EXECUTABLE=$VIRTUAL_ENV/bin/python
    -D BUILD_opencv_python2=OFF
    -D BUILD_opencv_python3=ON
    -D INSTALL_PYTHON_EXAMPLES=ON
    -D INSTALL_C_EXAMPLES=OFF
    -D BUILD_EXAMPLES=ON ..

git clone https://github.com/opencv/opencv

git clone https://github.com/opencv/opencv_contrib

[ 84%] Linking CXX executable ../../bin/opencv_perf_stitching
[ 84%] Built target opencv_perf_stitching
make: *** [all] Error 2