Insufficient permission not reported as an Error

[Busyvar]

Given : User is on linux, has no root privilege, has iw installed
When : User ask for scan
Then : User receive an empty list.

Expected behaviour : a specific error is returned.

iw require specific permission to launch scan subcommand.
quickfix suggest : after sending iw scan command, check exit status. It's 0 when scan has been operated properly and 255 when there is insuficient permission.