[Dy2St]Fix abnormal format of message when raise KeyError in Dy2St (#44996)

* Fix abnormal format of message when raise KeyError in Dy2St

* Format code

* Format code

* Add UT

* Rename method

python/paddle/fluid/dygraph/dygraph_to_static/error.py

@@ -143,6 +143,10 @@ class SuggestionDict(object):
         return self.suggestion_dict[key]
 
 
+class Dy2StKeyError(Exception):
+    pass
+
+
 class ErrorData(object):
     """
     Error data attached to an exception which is raised in un-transformed code.
@@ -159,6 +163,9 @@ class ErrorData(object):
 
     def create_exception(self):
         message = self.create_message()
+        if self.error_type is KeyError:
+            new_exception = Dy2StKeyError(message)
+        else:
             new_exception = self.error_type(message)
         setattr(new_exception, ERROR_DATA, self)
         return new_exception

python/paddle/fluid/tests/unittests/dygraph_to_static/test_error.py

@@ -443,6 +443,20 @@ class TestSuggestionErrorInRuntime(TestErrorBase):
         for disable_new_error in [0, 1]:
             self._test_raise_new_exception(disable_new_error)
 
+@paddle.jit.to_static
+def func_ker_error(x):
+    d = {
+        'x': x
+    }
+    y = d['y'] + x
+    return y
+
+class TestKeyError(unittest.TestCase):
+    def test_key_error(self):
+        paddle.disable_static()
+        with self.assertRaises(error.Dy2StKeyError):
+            x = paddle.to_tensor([1])
+            func_ker_error(x)
 
 if __name__ == '__main__':
     unittest.main()