System information:
Ubuntu 16.04, Anaconda 1.6.9, Python 3.6.4, libopencv 3.4.1, opencv 3.4.1, py-opencv 3.4.1.
Problem definition: I just upgraded my opencv to 3.4 through anaconda and found could not import.
The import error is: ImportError: anaconda3/lib/python3.6/site-packages/../../libopencv_dnn.so.3.4: undefined symbol: _ZNK6google8protobuf7Message25InitializationErrorStringB5cxx11Ev