Message 405791 - Python tracker

Thanks for looking into this so swiftly!

As a user, I have found PEP515 to be worded a little ambiguously with regards to formatting using underscores as thousands separators. While it enumerates a collection of types as far as the constructor is concerned, it does not do so for formatting. Instead, it says to support `_` as thousands separator for formatting wherever `,` is allowed. Since `,` does work for Decimal, I have taken that to imply `_` should work for Decimal as well.