added one line

sagemath · May 26, 2019 · b31f288 · b31f288
1 parent ac4ff86
commit b31f288
Showing 1 changed file with 2 additions and 1 deletion.
diff --git a/src/sage/graphs/base/c_graph.pyx b/src/sage/graphs/base/c_graph.pyx
@@ -2195,7 +2195,8 @@ cdef class CGraphBackend(GenericGraphBackend):
             sage: G.distance(0, 5, by_weight=true)
             3
         """
-
+        if exclude_vertices and (x in exclude_vertices or y in exclude_vertices):
+            raise LookupError("No path between %s and %s" % (x, y))
         if x == y:
             return 0