"InvalidRequirement: Invalid requirement, parse error" error after updating a python package

Question

After updating a package (IPython in my case) using pip install -U ipython running any Python script that uses entry points fails with this error:

Traceback (most recent call last):
  File "/home/adrian/dev/indico/env/bin/indico", line 5, in <module>
    from pkg_resources import load_entry_point
  ...
  File "/home/adrian/dev/indico/env/lib/python2.7/site-packages/pkg_resources/_vendor/packaging/requirements.py", line 94, in __init__
    requirement_string[e.loc:e.loc + 8], requirement_string))
pkg_resources._vendor.packaging.requirements.InvalidRequirement: Invalid requirement, parse error at "'< 2.0'"

Nothing else changed, I did not update any other libraries.

Answer 1

This is caused by an issue in setuptools==20.2.1 which is pulled in by IPython (setuptools>..), so a pip install -U updated it.

Until a fixed version is released or the broken version is pulled from PyPI there is a simple workaround (but note that it will break again if something updates setuptools):

• pip install -U pip
• pip uninstall setuptools
• pip install 'setuptools<20.2'

The pip update is needed since older versions of pip will not work without setuptools being installed

---

See these IRC logs and BitBucket issue for details:

• http://chat-logs.dcpython.org/day/pypa/2016-02-25
• https://bitbucket.org/pypa/setuptools/issues/502/packaging-164-does-not-allow-whitepace

Answer 2

Try downgrading your pip to 8.1.1:

pip install pip==8.1.1

That solved it for me.