[config] fix assert message (#1734)

deepspeed/runtime/config.py

@@ -995,8 +995,8 @@ class DeepSpeedConfig(object):
         ), f"Gradient accumulation steps: {grad_acc} has to be greater than 0"
 
         assert train_batch == micro_batch * grad_acc * self.world_size, (
-            f"Check batch related parameters. train_batch_size is not equal"
-            " to micro_batch_per_gpu * gradient_acc_step * world_size"
+            f"Check batch related parameters. train_batch_size is not equal "
+            "to micro_batch_per_gpu * gradient_acc_step * world_size "
             f"{train_batch} != {micro_batch} * {grad_acc} * {self.world_size}"
         )