Fix OpenBSD compilation issue caused by disabled ErrorKind "use"

[n1000]

Compilation error seen in this block:

        /// Enumerating serial ports on this platform is not supported
        pub fn available_ports() -> Result<Vec<SerialPortInfo>> {
            Err(Error::new(
                ErrorKind::Unknown,
                "Not implemented for this OS",
            ))
        }

[sirhcel]

Thank you very much for finding this issue and your contribution!

[sirhcel]

Thank you very much for your contribution! And please excuse our sluggish response time.

The fix builds with the existing targets and I will try to get a CI build for OpenBSD back.

[sirhcel]

I learned that OpenBSD is currently just a tier 3 target for Rust and not available through rustup yet. So I see no trivial path for adding this target to our CI builds. In favor of getting your fix into the next path release (#70), I'd like to postpone adding CI builds for OpenBSD (with #71 or even a later issue).

Do you know of an OpenBSD CI build for Rust where I could have a look at @n1000?

Thank you very much for spotting this issue. Please keep your eyes open in the meanwhile. ;-)