Fixed more Flake8 errors by removing debugging code.

theano/gof/opt.py

@@ -3010,15 +3010,9 @@ def check_stack_trace(f_or_fgraph, ops_to_check='last', bug_print='raise'):
         else:
             raise ValueError('The string bug_print is not recognised')
 
-    print("apply_nodes_to_check")
-    print(apply_nodes_to_check)
     for node in apply_nodes_to_check:
         for output in node.outputs:
-            print('Checking node')
-            print (node)
             if (not hasattr(output.tag, 'trace') or not output.tag.trace):
-                print ('Failed on node')
-                print (node)
                 return False
 
     return True