INFO: This is taking longer than usual. You might need to provide the dependency resolver with stric

ubuntu安装rasa

1、创建并激活虚拟环境
conda create -n rasa python=3.6
source activate rasa
2、安装rasa
pip3 install rasa

报错：

INFO: This is taking longer than usual. You might need to provide the dependency resolver with stricter constraints to reduce runtime. If you want to abort this run, you can press Ctrl + C to do so. To improve how pip performs, tell us what happened here: https://pip.pypa.io/surveys/backtracking

信息：这比平时花费的时间更长。您可能需要为依赖项解析器提供更严格的约束，以减少运行时。如果您想中止此运行，您可以按Ctrl+C来这样做。为了改进pip的性能，请告诉我们这里发生了什么：https://pip.pypa.io/surveys/backtracking

解决办法：

python -m pip install --upgrade pip
pip install -i http://mirrors.aliyun.com/pypi/simple/ --trusted-host mirrors.aliyun.com rasa