title: Matplotlib issue on OS X ("ImportError: cannot import name _thread")
body: <p>At some point in the last few days, Matplotlib stopped working for me on OS X. Here's the error I get when trying to <code>import matplotlib</code>:</p>
  
  <pre><code>Traceback (most recent call last):
    File "/my/path/to/script/my_script.py", line 15, in &lt;module&gt;
      import matplotlib.pyplot as plt
    File "/Library/Python/2.7/site-packages/matplotlib/pyplot.py", line 34, in &lt;module&gt;
      from matplotlib.figure import Figure, figaspect
    File "/Library/Python/2.7/site-packages/matplotlib/figure.py", line 40, in &lt;module&gt;
      from matplotlib.axes import Axes, SubplotBase, subplot_class_factory
    File "/Library/Python/2.7/site-packages/matplotlib/axes/__init__.py", line 4, in &lt;module&gt;
      from ._subplots import *
    File "/Library/Python/2.7/site-packages/matplotlib/axes/_subplots.py", line 10, in &lt;module&gt;
      from matplotlib.axes._axes import Axes
    File "/Library/Python/2.7/site-packages/matplotlib/axes/_axes.py", line 22, in &lt;module&gt;
      import matplotlib.dates as _  # &lt;-registers a date unit converter
    File "/Library/Python/2.7/site-packages/matplotlib/dates.py", line 126, in &lt;module&gt;
      from dateutil.rrule import (rrule, MO, TU, WE, TH, FR, SA, SU, YEARLY,
    File "/Library/Python/2.7/site-packages/dateutil/rrule.py", line 14, in &lt;module&gt;
      from six.moves import _thread
  ImportError: cannot import name _thread
  </code></pre>
  
  <p>The only system change I can think of was the Apple-forced NTP update and maybe some permission changes I did in /usr/local to get Brew working again.</p>
  
  <p>I tried reinstalling both Matplotlib and Python-dateutil via Pip, but this did not help.  Also tried a reboot.  I'm running Python 2.7.6, which is located in /usr/bin/python.  I'm running Yosemite (OS X 10.10.1).</p>