This was seen intermittently

diff -Naur networkx-1.8.1.orig/networkx/algorithms/assortativity/correlation.py networkx-1.8.1/networkx/algorithms/assortativity/correlation.py
--- networkx-1.8.1.orig/networkx/algorithms/assortativity/correlation.py	2013-08-04 13:53:31.000000000 +0000
+++ networkx-1.8.1/networkx/algorithms/assortativity/correlation.py	2014-03-17 11:11:25.710772149 +0000
@@ -115,7 +115,7 @@
     --------
     >>> G=nx.path_graph(4)
     >>> r=nx.degree_pearson_correlation_coefficient(G) 
-    >>> r 
+    >>> print("%.1f"%r)
     -0.5
 
     Notes