Facing error with OpenCV in Ubuntu?

cv2.error: OpenCV(3.4.2) /tmp/build/80754af9/opencv-suite_1535558553474/work/modules/highgui/src/window.cpp:632: error: (-2:Unspecified error) Rebuild the library with Windows, GTK+ 2.x or Carbon support. If you are on Ubuntu or Debian, install libgtk2.0-dev and pkg-config, then re-run cmake or configure script in function 'cvShowImage'.

Is this what you got as error ?

To solve this problem

Install cmake

sudo snap install cmake --classic

Still facing the problem ?
Try installing

sudo apt install libgtk2.0-dev
sudo apt install pkg-config
sudo apt install libopencv-*

Error
QObject::moveToThread: Current thread (0x5618076ecfe0) is not the object's thread (0x561807941d80). Cannot move to target thread (0x5618076ecfe0)

If you are using anaconda then try installing pyqt

conda install pyqt

I hope it helped you :)