Fix check on dy's number of dimensions

Signed-off-by: João Victor Tozatti Risso <joaovictor.risso@gmail.com>

Fix check on dy's number of dimensions
2fbf72fa · João Victor Tozatti Risso · 9181d894 · 2fbf72fa
--- a/theano/gpuarray/dnn.py
+++ b/theano/gpuarray/dnn.py
@@ -2982,8 +2982,8 @@ class GpuDnnTransformerGradI(DnnBase):
        grid_dims = as_tensor_variable(desc.owner.inputs[0])
        dy = as_gpuarray_variable(dy, context_name)
-        if img.ndim != 4:
+        if dy.ndim != 4:
-            raise TypeError('img must have 4 dimensions.')
+            raise TypeError('dy must have 4 dimensions.')
        dimg = GpuArrayType(dtype=img.dtype,
                            broadcastable=img.type.ndim * (False,),