OpenPCDet demo.py踩坑

安装spconv时出现一个问题的解决办法：
https://github.com/traveller59/spconv/issues/301

运行demo.py时报错：

ImportError: Could not import backend for traitsui.  Make sure you have a suitable UI toolkit like PyQt/PySide or wxPython installed.

解决方法如下：
先安装PyQt5：

pip install PyQt5

下面这个可以尝试一下，但是不凑效：

export QT_DEBUG_PLUGINS=1

再安装这个：

sudo apt-get install libxcb-xinerama0

参考：
https://blog.csdn.net/u012308586/article/details/108509503
https://blog.csdn.net/qq_36917144/article/details/111165983?utm_medium=distribute.pc_relevant.none-task-blog-baidujs_title-1&spm=1001.2101.3001.4242

此时运行demo.py在import torch时还可能报错：

ImportError: /usr/lib/x86_64-linux-gnu/libstdc++.so.6: version `CXXABI_1.3.11' not found (required by /home/PJLAB/liujunjie/anaconda3/envs/torch1.6/lib/python3.6/site-packages/torch/lib/libtorch_python.so)

需要把demo.py中的import torch位置放在import mayavi.mlab as mlab之前。

mayavi报错解决办法：

uninstall all pyqt5 packages in pip.
install qt and qtconsole in conda.

https://github.com/open-mmlab/OpenPCDet/issues/482