安装Scrapy出现six模块安装错误的解决办法

安装Scrapy的时候，要安装six模块，出现了下面的错误：

Uninstalling six-1.4.1:
Exception:
Traceback (most recent call last):
  File "/Library/Python/2.7/site-packages/pip-8.0.2-py2.7.egg/pip/basecommand.py", line 209, in main
    status = self.run(options, args)
  File "/Library/Python/2.7/site-packages/pip-8.0.2-py2.7.egg/pip/commands/install.py", line 317, in run
    prefix=options.prefix_path,
  File "/Library/Python/2.7/site-packages/pip-8.0.2-py2.7.egg/pip/req/req_set.py", line 725, in install
    requirement.uninstall(auto_confirm=True)
  File "/Library/Python/2.7/site-packages/pip-8.0.2-py2.7.egg/pip/req/req_install.py", line 752, in uninstall
    paths_to_remove.remove(auto_confirm)
  File "/Library/Python/2.7/site-packages/pip-8.0.2-py2.7.egg/pip/req/req_uninstall.py", line 115, in remove
    renames(path, new_path)
  File "/Library/Python/2.7/site-packages/pip-8.0.2-py2.7.egg/pip/utils/__init__.py", line 266, in renames
    shutil.move(old, new)
  File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/shutil.py", line 302, in move
    copy2(src, real_dst)
  File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/shutil.py", line 131, in copy2
    copystat(src, dst)
  File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/shutil.py", line 103, in copystat
    os.chflags(dst, st.st_flags)
OSError: [Errno 1] Operation not permitted: '/tmp/pip-IBLBtm-uninstall/System/Library/Frameworks/Python.framework/Versions/2.7/Extras/lib/python/six-1.4.1-py2.7.egg-info'

进入Python命令行模式import six是正常的，看样子是卸载1.4.1版本的时候出现了错误，网上搜索找到了解决办法：

sudo pip install scrapy --upgrade --ignore-installed six

PS：参考连接https://github.com/pypa/pip/issues/3165