python MARKER_EXPR = originalTextFor(MARKER_EXPR())("marker") TypeError: __call__() takes exactly 2

在安装cffi模块时，报了一下错误：

[root@localhost blog]# pip install cffi

Traceback (most recent call last):

  File "/usr/bin/pip", line 5, in <module>

    from pkg_resources import load_entry_point

  File "/usr/lib/python2.7/site-packages/pkg_resources/__init__.py", line 72, in <module>

    import packaging.requirements

  File "/usr/lib/python2.7/site-packages/packaging/requirements.py", line 59, in <module>

    MARKER_EXPR = originalTextFor(MARKER_EXPR())("marker")
TypeError: __call__() takes exactly 2 arguments (1 given)

尝试升级pip:

python -m pip install --upgrade --force pip

发现还是不行

后面对setuptool进行升级：

pip install setuptools==33.1.1

再重新安装cffi就可以了