Gentoo's Bugzilla –
Attachment 443886 Details for
Bug 591852kde-apps/libkface-16.04.3: CMake Error at /usr/share/opencv/OpenCVModules.cmake:114 (message): The imported target "opencv_core" references the file "/usr/lib64/libopencv_core.so.2.4.9" but this file does not exist.