title: Can't enable py-bt for gdb
body: <p>I have downloaded and compiled Python 3.5 on a CentOS 6.5 machine. It works without problems. The problem is I have to use <code>gdb</code> to debug a subtle bug involving cpu overuse during my python program execution.</p>
  
  <p>From official Python documentation about <a href="https://docs.python.org/devguide/gdb.html" rel="noreferrer">gdb extension</a>, they says the only thing to do is to add </p>
  
  <p><code>add-auto-load-safe-path /path/to/dir/with/python-gdb.py</code></p>
  
  <p>to <code>~/.gdbinit</code>. I tested it with</p>
  
  <pre><code>gdb --args /path/to/python3.5/binary
  (gdb) py-bt
  </code></pre>
  
  <p>but I get</p>
  
  <pre><code>Undefined command: "py-bt"
  </code></pre>
  
  <p><code>gdb</code> is version 7.2 and have python support enabled.</p>