can't use networkx.read_dot()

edit

When trying the following

import networkx
networkx.read_dot("foo.dot")

I get

ImportError                               Traceback (most recent call last)

/home/bla/tmp/<ipython console> in <module>()

/local/usr/share/sage/local/lib/python/networkx/drawing/nx_agraph.pyc in read_dot(path)
    197     except ImportError:
    198         raise ImportError, \
--> 199           "read_dot() requires pygraphviz: http://networkx.lanl.gov/pygraphviz"
    200     A=pygraphviz.AGraph(file=path)
    201     return from_agraph(A)

ImportError: read_dot() requires pygraphviz: http://networkx.lanl.gov/pygraphviz

It seems that I'm missing something really simple here. After a fair time browsing the documentation, however, I couldn't find what :(

Thanks in advance.