启动vim打开文件时出错：
The ycmd server SHUT DOWN (restart with ':YcmRestartServer'). YCM core library compiled for Python 2 but loaded in Python 3. Set the 'g:ycm_server_pytho
n_interpreter' option to a Python 2 interpreter path.
原因：
参照官网github上的文档编译命令：cmake -G "Unix Makefiles" -DPATH_TO_LLVM_ROOT=~/ycm_temp/llvm_root_dir . ~/.vim/bundle/YouCompleteMe/third_party/ycmd/cpp，默认使用的是python2
解决方案：
关闭使用python2的默认行为，关闭宏USE_PYTHON2，如下：
cmake -G "Unix Makefiles" -DPATH_TO_LLVM_ROOT=~/ycm_temp/llvm_root_dir -DUSE_PYTHON2=OFF . ~/.vim/bundle/YouCompleteMe/third_party/ycmd/cpp/
参考：
https://github.com/Valloric/YouCompleteMe#intro