System information (version)

I encountered this issue when I use dnn library to read yolov4 cfg and weight file.

net = cv.dnn.readNetFromDarknet(FLAGS.config, FLAGS.weights)

cv2.error: OpenCV(4.2.0) /io/opencv/modules/dnn/src/darknet/darknet_io.cpp:686: error: (-212:Parsing error) Unsupported activation: mish in function 'ReadDarknetFromCfgStream'