Make sure to disable compute_test_values for OutputGuard in DebugMode.

theano/compile/debugmode.py

@@ -28,6 +28,7 @@ from theano.compile.function_module import (
     std_fgraph)
 from theano.compile.mode import Mode, register_mode
 from theano.compile.ops import OutputGuard, _output_guard
+from theano.configparser import change_flags
 
 
 __docformat__ = "restructuredtext en"
@@ -2286,7 +2287,8 @@ class _Maker(FunctionMaker):  # inheritance buys a few helper functions
             fgraph.attach_feature(gof.DestroyHandler())
         for o in fgraph.outputs:
             try:
-                fgraph.replace_validate(o, _output_guard(o), reason='output_guard')
+                with change_flags(compute_test_value='off'):
+                    fgraph.replace_validate(o, _output_guard(o), reason='output_guard')
                 raise Exception("Output variable %s required output_guard, "
                                 "how was this output left unprotected against "
                                 "destructive operations?" % o)