title: python - igraph plot not available (cairo already installed)
body: <p>I've installed py2cairo using brew, but keep getting errors when trying to plot with igraph. I get the following error:</p>
  
  <pre><code>&gt;&gt;&gt; import igraph as ig
  &gt;&gt;&gt; from igraph import *
  &gt;&gt;&gt; UG = ig.Graph()
  &gt;&gt;&gt; UG.add_vertex('a')
  &gt;&gt;&gt; UG.add_vertex('b')
  &gt;&gt;&gt; UG.add_vertex('c')
  &gt;&gt;&gt; UG.add_vertex('d')
  &gt;&gt;&gt; UG.add_edge('a','d')
  &gt;&gt;&gt; UG.add_edge('a','c')
  &gt;&gt;&gt; UG.add_edge('b','c')
  &gt;&gt;&gt; UG.add_edge('b','a')
  
  &gt;&gt;&gt; layout = UG.layout_kamada_kawai()
  &gt;&gt;&gt; plot(UG,layout = layout)
  Traceback (most recent call last):
    File "&lt;stdin&gt;", line 1, in &lt;module&gt;
    File ".../anaconda/lib/python2.7/site-packages/igraph/drawing/__init__.py", line 427, in plot
      result = Plot(target, bbox, background="white")
    File ".../anaconda/lib/python2.7/site-packages/igraph/drawing/__init__.py", line 122, in __init__
      self._surface_was_created = not isinstance(target, cairo.Surface)
    File ".../anaconda/lib/python2.7/site-packages/igraph/drawing/utils.py", line 396, in __getattr__
      raise TypeError("plotting not available")
  TypeError: plotting not available
  </code></pre>