但是torch和torchvision的版本不匹配，于是把torchvision改成了0.6.1，这样安装时没问题的。但是之后再安装rknn_toolkit-1.7.0-cp36-cp36m-linux_x86_64.whl就又会有问题，卡在了这里。
Building wheel for onnx-tf (setup.py) ... done
Created wheel for onnx-tf: filename=onnx_tf-1.2.1-py3-none-any.whl size=162490 sha256=4306556a89a742eb6e6959771169fa68307a4354dc92ac2bffc44dc3d7fd7da2
Stored in directory: /tmp/pip-ephem-wheel-cache-qfnvs68s/wheels/7b/3e/03/27450a3e1a844d357fe400fd7e5f99e688ea2de274eddb194f
Building wheel for psutil (setup.py) ... done
Created wheel for psutil: filename=psutil-5.6.2-cp36-cp36m-linux_x86_64.whl size=264968 sha256=66e3f33d9f6d71dab263175badee729ddd4dbad9a6a0b431feb2fbaec33a7b1e
Stored in directory: /tmp/pip-ephem-wheel-cache-qfnvs68s/wheels/e5/47/9a/0d327e4099a54004c1c8c86cacf86bfb11b6929de5c3c707b5
Building wheel for sklearn (setup.py) ... done
Created wheel for sklearn: filename=sklearn-0.0-py2.py3-none-any.whl size=1310 sha256=b0a9548da7752ed9a12781bb8f7b2261714f9316602f6f9e94ddeaf54ddd3df9
Stored in directory: /tmp/pip-ephem-wheel-cache-qfnvs68s/wheels/14/73/eb/5fcf287e70cdb3c4948a20fe0209824d7fca5de4024a0e7598
Building wheel for opencv-python (PEP 517) ... /^[///