add IUserFriendlyError adapter for violation of check constraints
This way we get back the same error messages we get from the python
check.
Related to #5154406
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))