Use more specific error

[radarhere]

I was just looking at

Pillow/Tests/test_file_jpeg2k.py

Lines 338 to 342 in e7c1da3

	def test_unbound_local() -> None:
	# prepatch, a malformed jp2 file could cause an UnboundLocalError exception.
	with pytest.raises(OSError):
	with Image.open("Tests/images/unbound_variable.jp2"):
	pass

which triggers a SyntaxError

Pillow/src/PIL/Jpeg2KImagePlugin.py

Lines 205 to 207 in e7c1da3

	if size is None or mode is None:
	msg = "Malformed JP2 header"
	raise SyntaxError(msg)

and wondering why that didn't lead to an UnidentifiedImageError.

The answer was that it did, but UnidentifiedImageError inherits from OSError, so the test passed without a problem.

Pillow/src/PIL/__init__.py

Line 77 in e7c1da3

class UnidentifiedImageError(OSError):

This PR just updated the test to check for UnidentifiedImageError, to be clearer.