Kind of fixed Melanie's "Exception(sql)" correction

Throwing an Ex. with SQL command in the message looks weird,
this is a bit better, but I'm still not sure if that's the
proper way to handle.  Also, there is a catch one level up,
so is this one necessary?

OpenSim/Data/Migration.cs

@@ -150,9 +150,9 @@ namespace OpenSim.Data
                     {
                         cmd.ExecuteNonQuery();
                     }
-                    catch
+                    catch(Exception e)
                     {
-                        throw new Exception(sql);
+                        throw new Exception(e.Message + " in SQL: " + sql);
                     }
                 }
             }