Solved Fred's comments

theano/gof/op.py

@@ -622,7 +622,7 @@ class PureOp(object):
                         detailed_err_msg = utils.get_variable_trace_string(ins)
 
                         raise ValueError(
-                            'Cannot compute test value: input %i (%s) of Op %s missing default value. %s' %
+                            'Cannot compute test value: input %i (%s) of Op %s missing default value. \nStacktrace when the variable was created: %s' %
                             (i, ins, node, detailed_err_msg))
                     elif config.compute_test_value == 'ignore':
                         # silently skip test

theano/gof/utils.py

@@ -101,7 +101,7 @@ def add_tag_trace(thing, user_line=None):
              "theano/scan_module/", "theano\\scan_module\\",
              "theano/sparse/", "theano\\sparse\\",
              "theano/typed_list/", "theano\\typed_list\\"]
-    skips = []
+    
     tr = simple_extract_stack(limit=user_line, skips=skips)
     # Different python version use different sementic for
     # limit. python 2.7 include the call to extrack_stack. The -1 get

theano/tensor/nnet/tests/test_bn.py

@@ -66,12 +66,6 @@ def test_bn():
     m = theano.tensor.vector('m')
     v = theano.tensor.vector('v')
 
-    x.tag.test_value = numpy.random.rand(2, 2)
-    b.tag.test_value = numpy.random.rand(2)
-    g.tag.test_value = numpy.random.rand(2)
-    m.tag.test_value = numpy.random.rand(2)
-    v.tag.test_value = numpy.random.rand(2)
-
     bn_ref_op = bn_ref(x, g, b, m, v)
     f_ref = theano.function([x, b, g, m, v], [bn_ref_op])
     res_ref = f_ref(X, G, B, M, V)