Need to report a decent error if the user doesn't have permissions for a serial port

[mrstegeman]

By default (under ubuntu) you need to be root or a member of the dialout group in order to open the serial port.

If the user doesn't have sufficient permissions then we should detect this and report a reasonable error.

Requires WebThingsIO/gateway#877

[Swaagie]

@mrstegeman The first (partial) fix for this is in systemd systemd/systemd#14959 (comment). Just ran into the same issue a bit different. serialport uses udevadm info -e under the hood to list available ports. However udevadm didn't emit any errors and only exits with code 1. The second step here would be getting serialport to listen for the errors (or at minimum exit code 1 on finish) https://github.com/serialport/node-serialport/blob/258574260f312cdeb81bb265a437762f8e5e0ae4/packages/bindings/lib/linux-list.js#L43.

I'll open a PR against serialport to at rejecton exit code 1 as I'm unsure how fast different distro's will pickup on the improved systemd. From source code it seems that both darwin and w32 use async/await and should throw on error.

After serialport merges the PR, gateway should technically be able to reject based on errors.

[Swaagie]

serialport/node-serialport#2046 is now a thing and list should reject with an error