使用conda安装命令时一直出现问题，因为从2019年4月添加的国内镜像都不能用了

安装过程中出现以下问题：（历尽千辛万苦，终于才查到原来是清华源，腾讯源都不能用了）
The remote server could not find the noarch directory for the
requested channel with url: file:///C:/Miniconda36-x64/conda-bld
As of conda 4.3, a valid channel must contain a `noarch/repodata.json` and
associated `noarch/repodata.json.bz2` file, even if `noarch/repodata.json` is
empty. please request that the channel administrator create
`noarch/repodata.json` and associated `noarch/repodata.json.bz2` files.
$ mkdir noarch
$ echo '{}' > noarch/repodata.json
$ bzip2 -k noarch/repodata.json
You will need to adjust your conda configuration to proceed.

看新闻链接：https://www.linuxidc.com/Linux/2019-04/158330.htm

解决方法：

vim ～/.condarc    #查看配置文件

把之前添加的源都删掉，使用默认的就可以