Fix pickling and zip in Python 3.

theano/gof/fg.py

@@ -330,7 +330,7 @@ class FunctionGraph(utils.object2):
             if not used_or_output:
                 if not hasattr(apply_node.tag, 'removed_by'):
                     apply_node.tag.removed_by = []
-                apply_node.tag.removed_by.append(reason)
+                apply_node.tag.removed_by.append(str(reason))
                 self.apply_nodes.remove(apply_node)
                 self.variables.difference_update(apply_node.outputs)
                 self.execute_callbacks('on_prune', apply_node, reason)
@@ -421,7 +421,7 @@ class FunctionGraph(utils.object2):
             self.apply_nodes.add(node)
             if not hasattr(node.tag, 'imported_by'):
                 node.tag.imported_by = []
-            node.tag.imported_by.append(reason)
+            node.tag.imported_by.append(str(reason))
             for output in node.outputs:
                 self.__setup_r__(output)
                 self.variables.add(output)

theano/scan_module/scan_opt.py

@@ -202,7 +202,7 @@ def remove_constants_and_unused_inputs_scan(node):
         # DEBUG CHECK
         nwScan = scan_op.Scan(nw_inner, op_outs, nw_info)
         nw_outs = nwScan(*nw_outer, **dict(return_list=True))
-        return dict([("remove", [node])] + zip(node.outputs, nw_outs))
+        return dict([("remove", [node])] + list(zip(node.outputs, nw_outs)))
     else:
         return False