the command is oem-config-remove (note the dash) ...
if you call "oem-config remove" like you did above, you execute ubiquity in oem-config mode and hand the option "remove" to it, which will indeed result in a complaint from ubiquity ...
the command is oem-config-remove (note the dash) ...
if you call "oem-config remove" like you did above, you execute ubiquity in oem-config mode and hand the option "remove" to it, which will indeed result in a complaint from ubiquity ...