更新conda时出现AssertionError

我试图使用以下命令更新conda：

~$ conda update conda

它输出以下消息：

WARNING conda.base.context:use_only_tar_bz2(632): Conda is constrained to only 
using the old .tar.bz2 file format because you have conda-build installed, 
and it is <3.18.3.  Update or remove conda-build to get smaller downloads 
and faster extractions.
Collecting package metadata (repodata.json): done
Solving environment: - 

The environment is inconsistent, please check the package plan carefully

The following packages are causing the inconsistency:

- defaults/linux-64::cytoolz==0.9.0.1=py37h14c3975_1

- and around 100 more

Preparing transaction: done

Verifying transaction: done

Executing transaction: done

ERROR conda.core.link:_execute(637): An error occurred while installing 
package 'None'.

AssertionError()

Attempting to roll back.

Rolling back transaction: done

AssertionError()

我也尝试过

~$ conda update --all

但是它给了我和以前一样的错误。

关于这个问题，我发现一个解决方案虽然没有很好的解释，但是可以解决问题：

首先：使用命令：

~$ conda install anaconda 

这样就解决了环境不一致的问题。

第二：使用命令：

 ~$ conda update conda

该命令将毫无问题地执行，并且conda将会被更新。