成功解决：Warning： Python 3.6 was not found on your system… Neither ‘pyenv‘ nor ‘asdf‘ could be found to

在安装pipenv环境的时候：

pipenv install

出现如下错误：

Warning: Python 3.6 was not found on your system…
Neither 'pyenv' nor 'asdf' could be found to install Python.
You can specify specific versions of Python with:
$ pipenv --python path/to/python

通过执行以下命令来解决：

pipenv install --three