curtin: note the need for --extrausers on snappy.

subiquitycore/curtin.py

@@ -92,6 +92,8 @@ POST_INSTALL = '\n' + "\n".join(POST_INSTALL_LIST) + '\n'
 
 def curtin_configure_user(userinfo, dryrun=False):
     usercmds = []
+    # FIXME: snappy needs --extrausers too; should factor out a way to pass
+    #        additional parameters.
     usercmds += ["useradd -m -p {confirm_password} {username}".format(**userinfo)]
     if 'ssh_import_id' in userinfo:
         target = "/home/{username}/.ssh/authorized_keys".format(**userinfo)