conda install ... opencv, conda install ... opencv-python ruined my environment built on Windows 10. The error seemed to related to PyQt and authentication/path setting but couldn't specify the true cause.
So, instead of using anaconda binary, I tried unofficial windows binary and it worked :) The required steps are 1. Go to the site 2. Download .whl file appropriate for your environment, say RIGHT_BINARY.whl (opencv_python‑3.4.1‑cp36‑cp36m‑win_amd64.whl in my case) 3. install by pip install RIGHT_BINARY.whl
