title: Error in `/usr/bin/python': double free or corruption (out): 0x00007f7c3c017260
body: <p>I'm developing a website in Python using the (excellent) Flask framework. In the backend code I use APScheduler to run some cron-like jobs every minute, and I use Numpy to calculate some Standard Deviations. Don't know whether the usage of these modules matter, but I thought I'dd better mention them since I guess they might be the most likely to be the cause.</p>
  
  <p>Anyway, in the middle of operation, Python itself seemed to crash, giving the following:</p>
  
  <pre><code>*** Error in `/usr/bin/python': double free or corruption (out): 0x00007f7c3c017260 ***
  </code></pre>
  
  <p>I might be wrong, but as far as I know, this is pretty serious. So my question is actually; what could cause this, and how can I get more information about a crash like this? What does the <code>(out)</code> mean? I can't really reproduce this, but it happened 4 times in about 5 months now. I'm running the standard Python 2.7 on Ubuntu server 14.04</p>
  
  <p>I searched around and found a couple discussions about similar crashes, of which one thing comes back: concurrency seems to be related somehow (which is why I included the usage of APScheduler). </p>
  
  <p>If anybody has any idea how I could debug this or what could possibly be the cause of this; all tips are welcome!</p>