conda安装python-graphviz报错：

用conda安装python-graphviz时报错：CondaError: Cannot link a source that does not exist. C:\ProgramData\Anaconda3\Scripts\conda.exe

代码片段如下

pip-19.1.1-py3 100% |###############################| Time: 0:00:03 590.55 kB/s
ERROR conda.core.link:_execute_actions(337): An error occurred while installing package 'defaults::tqdm-4.32.1-py_0'.
CondaError: Cannot link a source that does not exist. C:\ProgramData\Anaconda3\Scripts\conda.exe
Attempting to roll back.


CondaError: Cannot link a source that does not exist. C:\ProgramData\Anaconda3\Scripts\conda.exe

求助如何解决

用pip试了，可以。在cmd下，pip install graphviz
anaconda prompt 下 conda install python-graphviz