我剛剛為MacOS X安裝了Python 3.6.1當我嘗試運行控制臺（或使用Python3運行任何命令）時，拋出此錯誤：  AttributeError: module 'enum' has no attribute 'IntFlag'$ /Library/Frameworks/Python.framework/Versions/3.6/bin/python3  Failed to import the site module  Traceback (most recent call last):    File "/usr/local/Cellar/python3/3.6.1/Frameworks/Python.framework/Versions/3.6/lib/python3.6/site.py", line 544, in <module>      main()    File "/usr/local/Cellar/python3/3.6.1/Frameworks/Python.framework/Versions/3.6/lib/python3.6/site.py", line 530, in main      known_paths = addusersitepackages(known_paths)    File "/usr/local/Cellar/python3/3.6.1/Frameworks/Python.framework/Versions/3.6/lib/python3.6/site.py", line 282, in addusersitepackages      user_site = getusersitepackages()    File "/usr/local/Cellar/python3/3.6.1/Frameworks/Python.framework/Versions/3.6/lib/python3.6/site.py", line 258, in getusersitepackages      user_base = getuserbase() # this will also set USER_BASE    File "/usr/local/Cellar/python3/3.6.1/Frameworks/Python.framework/Versions/3.6/lib/python3.6/site.py", line 248, in getuserbase      USER_BASE = get_config_var('userbase')    File "/usr/local/Cellar/python3/3.6.1/Frameworks/Python.framework/Versions/3.6/lib/python3.6/sysconfig.py", line 601, in get_config_var      return get_config_vars().get(name)    File "/usr/local/Cellar/python3/3.6.1/Frameworks/Python.framework/Versions/3.6/lib/python3.6/sysconfig.py", line 580, in get_config_vars      import _osx_support    File "/usr/local/Cellar/python3/3.6.1/Frameworks/Python.framework/Versions/3.6/lib/python3.6/_osx_support.py", line 4, in <module>      import re    File "/usr/local/Cellar/python3/3.6.1/Frameworks/Python.framework/Versions/3.6/lib/python3.6/re.py", line 142, in <module>      class RegexFlag(enum.IntFlag):  AttributeError: module 'enum' has no attribute 'IntFlag'  IntFlag類存在于enum.py中。那么，為什么會引發AttributeError？