mac下使用scrapy时出现的raise DistributionNotFound(req)异常的处理方法

在os x下，安装完python爬虫框架scrapy后，使用scrapy startproject tutorial新建scrapy项目时，出现以下问题：

Traceback (most recent call last):
  File "/usr/local/bin/scrapy", line 5, in <module>
    from pkg_resources import load_entry_point
  File "/System/Library/Frameworks/Python.framework/Versions/2.7/Extras/lib/python/pkg_resources.py", line 2603, in <module>
    working_set.require(__requires__)
  File "/System/Library/Frameworks/Python.framework/Versions/2.7/Extras/lib/python/pkg_resources.py", line 666, in require
    needed = self.resolve(parse_requirements(requirements))
  File "/System/Library/Frameworks/Python.framework/Versions/2.7/Extras/lib/python/pkg_resources.py", line 565, in resolve
    raise DistributionNotFound(req)  # XXX put more info here
pkg_resources.DistributionNotFound: queuelib

网上查了很久，终于找到解决方法（来自一位国际友人）：

This is a problem in pkg_resources, and can be fixed by: sudo pip install --upgrade setuptools.
It works fine with setuptools-5.3.