更新过程如下，使用命令conda update conda，清华镜像源。conda的版本比较老了，是2017年的，因为之前安装新版anaconda一直出现各种错误，只有2017年的版本能正常安装。所以现在想升级到最新版。另外下面系统提到的conda clean --packages指令也试过了，没有用。
(C:\ProgramData\Anaconda3) D:\用户目录\我的文档>conda update conda
Fetching package metadata ...........
Solving package specifications: .
Package plan for installation in environment C:\ProgramData\Anaconda3:
The following NEW packages will be INSTALLED:
conda-package-handling: 1.7.3-py36hb5e345e_0 conda-forge
tqdm: 4.62.2-pyhd8ed1ab_0 conda-forge
The following packages will be UPDATED:
conda: 4.3.30-py36h7e176b0_0 https://mirrors.tuna.tsinghua.
edu.cn/anaconda/pkgs/free --> 4.10.3-py36ha15d459_0 conda-forge
menuinst: 1.4.8-py36h870ab7d_0 defaults
--> 1.4.17-py36ha15d459_1 conda-forge
pycosat: 0.6.2-py36hf17546d_1 defaults
--> 0.6.3-py36h68aa20f_1006 conda-forge
Proceed ([y]/n)? y
ERROR conda.core.link:_execute_actions(337): An error occurred while installing
package 'conda-forge::tqdm-4.62.2-pyhd8ed1ab_0'.
CondaError: Cannot link a source that does not exist. C:\ProgramData\Anaconda3\S
cripts\conda.exe
Running `conda clean --packages` may resolve your problem.
Attempting to roll back.
CondaError: Cannot link a source that does not exist. C:\ProgramData\Anaconda3\S
cripts\conda.exe
Running `conda clean --packages` may resolve your problem.
(C:\ProgramData\Anaconda3) D:\用户目录\我的文档>
