[PLUGGABLE_BACKEND] Remove incorrect exception message matching.

[hertschuh]

The exception comes from here: https://github.com/keras-team/keras/blob/pluggable_backend/keras/src/export/saved_model_export_archive.py#L27-L28

The message matched in the unit tests was incorrect. However, this never came up because this test only runs from trainable backends. PaddlePaddle and MLX are the first trainable backends that do not support saved_model export.

Context: keras-team/keras-paddle#4

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[gemini-code-assist]

Code Review

This pull request modifies a test assertion in keras/src/models/model_test.py to use self.assertRaises instead of self.assertRaisesRegex. The review feedback correctly points out that this violates the Keras API design guidelines, which require using self.assertRaisesRegex to verify error message clarity, and suggests restoring the regex assertion with the appropriate error message.

[gemini-code-assist]

According to the Keras API design guidelines (under Testing -> Verify Error Clarity), we should use self.assertRaisesRegex to verify that the error message contains the expected guidance, rather than just using self.assertRaises.

Please update the assertion to use self.assertRaisesRegex with the correct expected exception message (e.g., matching "SavedModel export is not supported with backend").

Suggested change

	with self.assertRaises(NotImplementedError):
	with self.assertRaisesRegex(
	NotImplementedError,
	"SavedModel export is not supported with backend",
	):

References

1. Verify Error Clarity: Use self.assertRaisesRegex to verify that the error message contains the expected guidance. ^(link)

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
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Additional details and impacted files

@@                 Coverage Diff                  @@
##             pluggable_backend   #23547   +/-   ##
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  Coverage                     ?   84.84%           
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  Files                        ?      458           
  Lines                        ?    62462           
  Branches                     ?    10608           
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  Hits                         ?    52994           
  Misses                       ?     6781           
  Partials                     ?     2687           

Flag	Coverage Δ
keras	84.64% <ø> (?)
keras-cpu	83.81% <ø> (?)
keras-gpu	79.84% <ø> (?)
keras-jax	65.96% <ø> (?)
keras-numpy	61.07% <ø> (?)
keras-tensorflow	67.80% <ø> (?)
keras-torch	67.23% <ø> (?)
keras-tpu	65.65% <ø> (?)

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[jeffcarp]

Thanks!