问题描述：
在执行conda update conda、conda update anaconda或conda update --all时遇到错误：
RemoveError: 'requests' is a dependency of conda and cannot be removed from
conda's operating environment.
解决办法：
执行以下命令强制更新：
conda update --force conda
在执行conda update conda、conda update anaconda或conda update --all时遇到错误：
RemoveError: 'requests' is a dependency of conda and cannot be removed from
conda's operating environment.
执行以下命令强制更新：
conda update --force conda