SECURITY: prevent DoS when calling --help on commands using IRCParser

argparse's default behaviour is to exit after displaying --help and --version information. However, doing so freezes the current IRC listener and essentially allows for DoS via IRC...
This bug does not affect any released (stable) version of PyLInk - only commits after 93c9b6289c

utils.py

@@ -561,6 +561,9 @@ class IRCParser(argparse.ArgumentParser):
     def error(self, message):
         raise InvalidArgumentsError(message)
 
+    def exit(self, *args):
+        return
+
 class DeprecatedAttributesObject():
     """
     Object implementing deprecated attributes and warnings on access.