It drives me creazy as wpa_cli reports always

  "Failed to connect to non-global ctrl_ifname: (nil)  error: No such file or
directory"

and now I've found in the manual page (not installed in the ARM boot images)

         -u     Enable DBus control interface. If enabled, interface
                definitions  may  be  omitted.  (This  is  only  available
                if  wpa_supplicant  was  built  with  the
                CON-FIG_CTRL_IFACE_DBUS_NEW option.)

... means no sockets below /var/run/wpa_supplicant/ ... even no directory
/var/run/wpa_supplicant/ at all.

This makes wpa_cli as well ad wpa_gui useless ... or all tools have to be
movedd forward to use dbus address of the running wpa_ supplicant