ImportError: No module named extern : <p>I'm getting this error when trying to install any package with pip. I have two pip instances, one with Python 2.7 and other with Python 3.</p>

<pre><code>    Could not import setuptools which is required to install from a source distribution.
Traceback (most recent call last):
  File "/usr/local/lib/python2.7/dist-packages/pip/req/req_install.py", line 375, in setup_py
    import setuptools  # noqa
  File "/usr/local/lib/python2.7/dist-packages/setuptools/__init__.py", line 11, in &lt;module&gt;
    from setuptools.extern.six.moves import filterfalse, map
  File "/usr/local/lib/python2.7/dist-packages/setuptools/extern/__init__.py", line 1, in &lt;module&gt;
    from pkg_resources.extern import VendorImporter
ImportError: No module named extern
</code></pre>

<p>Even when I try to install the 'extern' module I get this error. Also when installing with Python itself, like <code>python setup.py install</code>.</p>

<p>Thanks in advance. </p>
