A property's `fdel` method is not invoked when `__delattr__` is overridden
<p>I have a class like this, in which I have declared a property <code>x</code>, and overridden <code>__delattr__</code>:</p>

<pre><code>class B(object):
    def __init__(self, x):
        self._x = x
    def _get_x(self):
        return self._x
    def _set_x(self, x):
        self._x = x
    def _del_x(self):
        print '_del_x'

    x = property(_get_x, _set_x, _del_x)

    def __delattr__(self, name):
        print '__del_attr__'
</code></pre>

<p>Now when I run</p>

<pre><code>   b = B(1)
   del b.x
</code></pre>

<p>Only <code>__del_attr__</code> get invoked, anybody knows why and how to solve this problem?</p>
