Fixed #11215 -- Replaced erroneous catch with except in testing doc.

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If you point the test client at a view that raises an exception, that exception

will be visible in the test case. You can then use a standard ``try...catch``

will be visible in the test case. You can then use a standard ``try...except``

block or ``unittest.TestCase.assertRaises()`` to test for exceptions.

The only exceptions that are not visible to the test client are ``Http404``,