ConfirmationDialog: Add css styling

gajim/data/style/gajim.css

@@ -338,3 +338,6 @@ popover.combo list { border-style: none; background-color: transparent; }
 popover.combo list > row { padding: 0px 12px 0px 12px; min-height: 50px; }
 popover.combo list > row:not(:last-child) { border-bottom: 1px solid alpha(#cdc7c2, 0.5); }
 popover.combo scrollbar.vertical { padding-top: 2px; padding-bottom: 2px; }
+
+
+messagedialog.confirmation-dialog > box { margin-top: 18px; }

gajim/gtk/dialogs.py

@@ -424,6 +424,8 @@ def __init__(self, title, text, sec_text, buttons,
                                    message_type=Gtk.MessageType.QUESTION,
                                    modal=modal)
 
+        self.get_style_context().add_class('confirmation-dialog')
+
         self._buttons = {}
 
         for button in buttons: