[web/request] clearly mark user_callback-related methods as deprecated
The deprecated decorator not only emits a warning at run-time
but above all makes the deprecation immediately apparent in the source.
closes #3567793.
import ConfigParser
try:
undo_actions = config.cfgfile_parser.get('MAIN', 'undo-support', False)
except ConfigParser.NoOptionError:
pass # this conf. file was probably already migrated
else:
config.global_set_option('undo-enabled', bool(undo_actions))