I was trying to install anaconda-navigator on macOS Mojave, but there was no meta-package for Python v 3.6. So, I tried to upgrade my python version to 3.8. There was an article by Matthew Broberg titled - "The right and wrong way to set up Python 3 as default on a Mac" (https://opensource.com/article/19/5/python-3-default-mac).
a) The first step was to invoke 'xcode-select --install'. Since, it was installed already.
I tried to 'brew -install pyenv'.
I got this error
'''
错误：以下公式：
git 不能作为二进制包安装，必须从源代码构建。
安装命令行工具：
xcode-select --install
错误：必须安装 Git 并在您的 PATH 中！
错误：以下公式：
pyenv
不能作为二进制包安装，必须从源代码构建。
安装命令行工具：
xcode-select --install
'''
b) 然后我跑了
'xcode-select --install'
Then I got a response
'code-select: note: install requested for command line developer tools'
There was a pop-up menu asking command line developer tools to be installed. I clicked OK. It installed fine.
c) Then I ran 'xcode-select --install'. I got a response saying that the command line tools was already installed.
d) Then I tried running
'brew install pyenv'
After a lengthy output which seemed fine, I got this error :
'/usr/local/Homebrew/Library/Homebrew/brew.rb:17:in `<main>': HOMEBREW_REQUIRED_RUBY_VERSION was not exported! Please call bin/brew directly! (RuntimeError)'
e) I was also not able to locate pyenv by using 'which pyenv'