random_rewire(): Raise warning if edge_probs is not supplied

src/graph_tool/generation/__init__.py

@@ -791,19 +791,6 @@ def random_rewire(g, model="configuration", n_iter=1, edge_sweep=True,
        no. 1: 016107 (2011) :doi:`10.1103/PhysRevE.83.016107` :arxiv:`1008.3926`
 
     """
-    # if not parallel_edges:
-    #     p = label_parallel_edges(g)
-    #     if p.a.max() != 0:
-    #         raise ValueError("Parallel edge detected. Can't rewire " +
-    #                          "graph without parallel edges if it " +
-    #                          "already contains parallel edges!")
-
-    # if not self_loops:
-    #     l = label_self_loops(g)
-    #     if l.a.max() != 0:
-    #         raise ValueError("Self-loop detected. Can't rewire graph " +
-    #                          "without self-loops if it already contains" +
-    #                          " self-loops!")
 
     if (edge_probs is not None and not g.is_directed()) and "blockmodel" not in model:
         corr = lambda i, j: edge_probs(i[1], j[1])
@@ -813,6 +800,8 @@ def random_rewire(g, model="configuration", n_iter=1, edge_sweep=True,
     if model not in ["probabilistic-configuration", "blockmodel",
                      "blockmodel-degree"]:
         g = GraphView(g, reversed=False)
+    elif edge_probs is None:
+        raise ValueError("A function must be supplied as the 'edge_probs' parameter")
 
     if model == "blockmodel-degree" and alias and edge_sweep:
         edge_sweep = False