`PyErr` conversion for `TryFromFloatSecsError` (and other missing stdlib errors?)

[davidhewitt]

I noticed we don't have a conversion to PyErr from TryFromFloatSecsError. It's probably trivial to add one to src/err/impls.rs.

I wonder if there are any (relatively) new standard library errors we currently lack, it might be interesting to audit.

[Harikeshav-R]

Looks like a conversion for TryFromFloatSecsError is very straightforward using the impl_to_pyerr! macro in src/err/impls.rs.

While looking into this, I did a quick audit and noticed we're also missing conversions for a few other standard library errors, such as:

• std::time::SystemTimeError
• std::path::StripPrefixError
• std::env::JoinPathsError
• std::char::ParseCharError
• std::char::CharTryFromError
• std::string::FromUtf16Error
• std::char::DecodeUtf16Error
• std::env::VarError

I'd be happy to submit a PR to add TryFromFloatSecsError along with the other easily mappable ones. Let me know if that sounds good.

[davidhewitt]

Sounds good to me, thanks.

The list you write generally seem reasonable to include. FromUtf16Error is not possible to add an implementation, we removed it recently in #5668, it was fundamentally broken. I also think std::env::VarError is nontrivial, it might be that it could convert to either of KeyError or ValeuError depending on its case, but I'm far from confident that's a good mapping.