Fix compatibility issue with python 2

src/graph_tool/__init__.py

@@ -2867,7 +2867,10 @@ for Vertex in libcore.get_vlist():
     Vertex.all_neighbours = _all_neighbours
     Vertex.in_degree = _in_degree
     Vertex.out_degree = _out_degree
-    Vertex.is_valid.__doc__ = "Returns ``True`` if the descriptor corresponds to an existing vertex in the graph, ``False`` otherwise."
+    try:
+        Vertex.is_valid.__doc__ = "Returns ``True`` if the descriptor corresponds to an existing vertex in the graph, ``False`` otherwise."
+    except AttributeError:
+        pass
     Vertex.__repr__ = _vertex_repr
     Vertex.__eq__ = v_eq
     Vertex.__ne__ = v_ne
@@ -2903,9 +2906,12 @@ for Edge in libcore.get_elist():
     Edge.__repr__ = _edge_repr
     Edge.__iter__ = _edge_iter
     Edge.__doc__ = _edge_doc
-    Edge.is_valid.__doc__ = "Returns ``True`` if the descriptor corresponds to an existing edge in the graph, ``False`` otherwise."
-    Edge.source.__doc__ = "Returns the source of the edge (a :class:`~graph_tool.Vertex` instance)."
-    Edge.target.__doc__ = "Returns the target of the edge (a :class:`~graph_tool.Vertex` instance)."
+    try:
+        Edge.is_valid.__doc__ = "Returns ``True`` if the descriptor corresponds to an existing edge in the graph, ``False`` otherwise."
+        Edge.source.__doc__ = "Returns the source of the edge (a :class:`~graph_tool.Vertex` instance)."
+        Edge.target.__doc__ = "Returns the target of the edge (a :class:`~graph_tool.Vertex` instance)."
+    except AttributeError:
+        pass
 
 # some shenanigans to make it seem there is only a single edge and vertex class
 EdgeBase.__doc__ = Edge.__doc__

src/graph_tool/collection/konect.py

@@ -25,7 +25,10 @@ if sys.version_info < (3,):
 
 import os.path
 import tempfile
-import urllib.request
+if sys.version_info < (3,):
+    from urllib2 import urlopen
+else:
+    from urllib.request import urlopen
 import tarfile
 import warnings
 import numpy
@@ -77,13 +80,13 @@ def load_koblenz_dir(dirname):
 
 def get_koblenz_network_data(name):
     with tempfile.TemporaryFile(mode='w+b') as ftemp:
-        with urllib.request.urlopen('http://konect.uni-koblenz.de/downloads/tsv/%s.tar.bz2' % name) as response:
-            buflen = 1 << 20
-            while True:
-                buf = response.read(buflen)
-                ftemp.write(buf)
-                if len(buf) < buflen:
-                    break
+        response = urlopen('http://konect.uni-koblenz.de/downloads/tsv/%s.tar.bz2' % name)
+        buflen = 1 << 20
+        while True:
+            buf = response.read(buflen)
+            ftemp.write(buf)
+            if len(buf) < buflen:
+                break
         ftemp.seek(0)
         with tempfile.TemporaryDirectory(suffix=name) as tempdir:
             with tarfile.open(fileobj=ftemp, mode='r:bz2') as tar: