`humility i2c` could maybe return a non-zero exit code when the I2C operation returns an error

I wanted to use a bash until loop to retry a humility i2c command until it succeeds, but it looks like humility i2c (and possibly also humility hiffy?) exits with 0 when it was able to successfully execute the hiffy IPC operation on the device, but the IPC returned an error. For example:

eliza@niles ~ $ pfexec humility -t gimlet-c i2c -b rear --device 0x20 --register 0x00 --nbytes 1 --timeout 10000
humility: attached to 0483:3754:000D00344741500820383733 via ST-Link V3
Controller I2C4, device 0x20, register 0x0 = Err(BusLocked)
eliza@niles ~ $ echo $?
0
eliza@niles ~ $

IMO, it would be a bit nicer for humility to exit with a non-zero exit code when the on-device operation fails. That way, the error is visible to the user's shell and you don't have to do things like grepping for the string that indicates an error...

Start at the Rust implementation of the humility i2c command and trace how the hiffy IPC result is converted into the CLI status. Reproduce the shown BusLocked example, then verify that device-operation errors return a non-zero shell status while successful operations still return zero; check whether humility hiffy follows the same path.