Raise Invalid for non-finite Number values

[CodingFeng101]

Fixes #541.

What changed

Number now rejects non-finite Decimal values such as Infinity and NaN with Invalid instead of leaking the internal TypeError from precision inspection.

Why

Number is a validator and callers expect validation failures to surface as voluptuous Invalid / MultipleInvalid. Non-finite numeric strings currently escape that contract when precision or scale checking is enabled.

Validation

• python -m pytest voluptuous\tests\tests.py::test_number_validation_with_string voluptuous\tests\tests.py::test_number_validation_with_non_finite_number voluptuous\tests\tests.py::test_number_validation_with_invalid_precision_invalid_scale -q
• python -m pytest voluptuous\tests\tests.py -q
• python -m py_compile voluptuous\validators.py voluptuous\tests\tests.py
• git diff --check

[alecthomas]

Thanks, but #542 already addresses this and was raised first.