OS: Debian 9.2.1 amd64
driver=rtl8192cu driverversion=4.9.0-4-amd64
/var/log/kern.log:
…
wlan0: aborting authentication with xx:xx:xx:xx:xx:xx by local choice (Reason: 3=DEAUTH_LEAVING)
…
Cause (in my case): REGDOMAIN variable in /etc/default/crda
Fix:
iw reg set NO
sed -i 's/^REG.*=$/&NO/' /etc/default/crda