macOS brew 更新后Python找不到md5

前几天，不知道干了啥，比较值得怀疑的是当时执行 brew install supervisor
更新了一堆应用程序，然后只要 cd ~
或者回车一下，就会吐出一堆错误来。

ERROR:root:code for hash md5 was not found.
Traceback (most recent call last):
  File "/usr/local/Cellar/python@2/2.7.16/Frameworks/Python.framework/Versions/2.7/lib/python2.7/hashlib.py", line 147, in 
    globals()[__func_name] = __get_hash(__func_name)
  File "/usr/local/Cellar/python@2/2.7.16/Frameworks/Python.framework/Versions/2.7/lib/python2.7/hashlib.py", line 97, in __get_builtin_constructor
    raise ValueError('unsupported hash type ' + name)
ValueError: unsupported hash type md5
ERROR:root:code for hash sha1 was not found.
Traceback (most recent call last):
  File "/usr/local/Cellar/python@2/2.7.16/Frameworks/Python.framework/Versions/2.7/lib/python2.7/hashlib.py", line 147, in 
    globals()[__func_name] = __get_hash(__func_name)
  File "/usr/local/Cellar/python@2/2.7.16/Frameworks/Python.framework/Versions/2.7/lib/python2.7/hashlib.py", line 97, in __get_builtin_constructor
    raise ValueError('unsupported hash type ' + name)
ValueError: unsupported hash type sha1
ERROR:root:code for hash sha224 was not found.
Traceback (most recent call last):
  File "/usr/local/Cellar/python@2/2.7.16/Frameworks/Python.framework/Versions/2.7/lib/python2.7/hashlib.py", line 147, in 
    globals()[__func_name] = __get_hash(__func_name)
  File "/usr/local/Cellar/python@2/2.7.16/Frameworks/Python.framework/Versions/2.7/lib/python2.7/hashlib.py", line 97, in __get_builtin_constructor
    raise ValueError('unsupported hash type ' + name)
ValueError: unsupported hash type sha224
ERROR:root:code for hash sha256 was not found.
Traceback (most recent call last):
  File "/usr/local/Cellar/python@2/2.7.16/Frameworks/Python.framework/Versions/2.7/lib/python2.7/hashlib.py", line 147, in 
    globals()[__func_name] = __get_hash(__func_name)
  File "/usr/local/Cellar/python@2/2.7.16/Frameworks/Python.framework/Versions/2.7/lib/python2.7/hashlib.py", line 97, in __get_builtin_constructor
    raise ValueError('unsupported hash type ' + name)
ValueError: unsupported hash type sha256
ERROR:root:code for hash sha384 was not found.
Traceback (most recent call last):
  File "/usr/local/Cellar/python@2/2.7.16/Frameworks/Python.framework/Versions/2.7/lib/python2.7/hashlib.py", line 147, in 
    globals()[__func_name] = __get_hash(__func_name)
  File "/usr/local/Cellar/python@2/2.7.16/Frameworks/Python.framework/Versions/2.7/lib/python2.7/hashlib.py", line 97, in __get_builtin_constructor
    raise ValueError('unsupported hash type ' + name)
ValueError: unsupported hash type sha384
ERROR:root:code for hash sha512 was not found.
Traceback (most recent call last):
  File "/usr/local/Cellar/python@2/2.7.16/Frameworks/Python.framework/Versions/2.7/lib/python2.7/hashlib.py", line 147, in 
    globals()[__func_name] = __get_hash(__func_name)
  File "/usr/local/Cellar/python@2/2.7.16/Frameworks/Python.framework/Versions/2.7/lib/python2.7/hashlib.py", line 97, in __get_builtin_constructor
    raise ValueError('unsupported hash type ' + name)
ValueError: unsupported hash type sha512

在网上找了N多资料，基本上没有用处。不过在 这里
看到重装python2会有用，就试了了下 brew reinstall python@2
，但brew会继续教做人。

...
==> Installing python@2
Error: An exception occurred within a child process:
  FormulaUnavailableError: No available formula with the name "/usr/local/opt/python@2/.brew/python@2.rb"

继续挖，有叫人从URL安装的， brew reinstall https://raw.githubusercontent.com/Homebrew/homebrew-core/94d572a132a63651739fef1931f540404b7eaa31/Formula/python@2.rb
，试了，可能会有用，但有个警告比较吓人：

Warning: Unsupported installation from a commit URL!
Consider using `brew extract python@2 ...` instead!"
This will extract your desired python@2 version to a stable tap instead of
installing from a commit URL that cannnot receive updates or fixes!

吓得我赶紧儿 Ctrl-C 取消掉。最后解决方式是先 brew uninstall python@2
，然后再 brew reinstall python@2
再次安装，就好了。