Refine the unittest to support py38 (#27208)

* Refine the unittest to support py38

    test=develop

python/paddle/fluid/tests/unittests/test_device_guard.py

@@ -33,6 +33,14 @@ def execute(main_program, startup_program):
     exe.run(main_program)
 
 
+def get_vaild_warning_num(warning, w):
+    num = 0
+    for i in range(len(w)):
+        if warning in str(w[i].message):
+            num += 1
+    return num
+
+
 class TestDeviceGuard(unittest.TestCase):
     def test_device_guard(self):
         main_program = fluid.Program()
@@ -133,7 +141,10 @@ class TestDeviceGuard(unittest.TestCase):
                         i = fluid.layers.increment(x=i, value=1, in_place=True)
                         fluid.layers.less_than(x=i, y=loop_len, cond=cond)
 
-        assert len(w) == 1
+        warning = "The Op(while) is not support to set device."
+        warning_num = get_vaild_warning_num(warning, w)
+        assert warning_num == 1
+
         all_ops = main_program.global_block().ops
         device_attr_name = core.op_proto_and_checker_maker.kOpDeviceAttrName()
         for op in all_ops:
@@ -169,7 +180,10 @@ class TestDeviceGuard(unittest.TestCase):
                         shape=[1], value=4.0, dtype='float32')
                     result = fluid.layers.less_than(x=x, y=y, force_cpu=False)
 
-        assert len(w) == 2
+        warning = "\'device_guard\' has higher priority when they are used at the same time."
+        warning_num = get_vaild_warning_num(warning, w)
+        assert warning_num == 2
+
         all_ops = main_program.global_block().ops
         device_attr_name = core.op_proto_and_checker_maker.kOpDeviceAttrName()
         for op in all_ops:

python/paddle/fluid/tests/unittests/test_gather_op.py

@@ -216,7 +216,7 @@ class API_TestGather(unittest.TestCase):
                       "index": index_np,
                       'axis': axis_np},
                 fetch_list=[out])
-            expected_output = gather_numpy(x_np, index_np, axis_np)
+            expected_output = gather_numpy(x_np, index_np, axis_np[0])
         self.assertTrue(np.allclose(result, expected_output))
 
 

python/paddle/fluid/tests/unittests/test_save_model_without_var.py

@@ -50,7 +50,7 @@ class TestSaveModelWithoutVar(unittest.TestCase):
                 params_filename='params')
             expected_warn = "no variable in your model, please ensure there are any variables in your model to save"
             self.assertTrue(len(w) > 0)
-            self.assertTrue(expected_warn == str(w[0].message))
+            self.assertTrue(expected_warn == str(w[-1].message))
 
 
 if __name__ == '__main__':