Hypothesis for Python - version 6.62.0

A classic error when testing is to write a test function that can
never fail, even on inputs that aren't allowed or manually provided.
By analogy to the design pattern of:

@pytest.mark.parametrize("arg", [
..., # passing examples
pytest.param(..., marks=[pytest.mark.xfail]) # expected-failing input
])

we now support "@example(...).xfail()", with the same (optional)
"condition", "reason", and "raises" arguments as
"pytest.mark.xfail()".

Naturally you can also write ".via(...).xfail(...)", or
".xfail(...).via(...)", if you wish to note the provenance of
expected-failing examples.

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