update error log for batch_norm_grad (#22017)

* update error information about batch_norm_grad

* update bn,test=develop

paddle/fluid/operators/batch_norm_op.cc

@@ -528,10 +528,18 @@ class BatchNormGradKernel<platform::CPUDeviceContext, T>
     const auto *saved_inv_variance = ctx.Input<Tensor>("SavedVariance");
     const std::string data_layout_str = ctx.Attr<std::string>("data_layout");
     const bool use_global_stats = ctx.Attr<bool>("use_global_stats");
+    const bool is_test = ctx.Attr<bool>("is_test");
     const float epsilon = ctx.Attr<float>("epsilon");
     const DataLayout data_layout =
         framework::StringToDataLayout(data_layout_str);
 
+    PADDLE_ENFORCE_EQ(
+        is_test, false,
+        platform::errors::InvalidArgument(
+            "`is_test = True` CANNOT be used in train program. If "
+            "you want to use global status in pre_train model, "
+            "please set `use_global_stats = True`"));
+
     // Get the size for each dimension.
     // NCHW [batch_size, in_channels, in_height, in_width]
     const auto &x_dims = x->dims();

paddle/fluid/operators/batch_norm_op.cu

@@ -423,6 +423,13 @@ class BatchNormGradKernel<platform::CUDADeviceContext, T>
     const auto *x = ctx.Input<Tensor>("X");
     const auto *d_y = ctx.Input<Tensor>(framework::GradVarName("Y"));
     const auto *scale = ctx.Input<Tensor>("Scale");
+    const bool is_test = ctx.Attr<bool>("is_test");
+    PADDLE_ENFORCE_EQ(
+        is_test, false,
+        platform::errors::InvalidArgument(
+            "`is_test = True` CANNOT be used in train program. If "
+            "you want to use global status in pre_train model, "
+            "please set `use_global_stats = True`"));
 
     const auto &x_dims = x->dims();
 

python/paddle/fluid/layers/nn.py

@@ -2461,6 +2461,7 @@ def batch_norm(input,
     Note:
         if build_strategy.sync_batch_norm=True, the batch_norm in network will use 
         sync_batch_norm automatically.
+        `is_test = True` can only be used in test program and inference program, `is_test` CANNOT be set to True in train program, if you want to use global status from pre_train model in train program, please set `use_global_stats = True`.
 
     Args:
         input(Variable): The rank of input variable can be 2, 3, 4, 5. The data type