code: function() {
      this.jsonInit({
        "message0": Blockly.Msg.CONTROL_REPEATUNTIL,
        "message1": "%1",
        "message2": "%1",
        "lastDummyAlign2": "RIGHT",
        "args0": [
          {
            "type": "input_value",
            "name": "CONDITION",
            "check": "Boolean"
          }
        ],
        "args1": [
          {
            "type": "input_statement",
            "name": "SUBSTACK"
          }
        ],
        "args2": [
          {
            "type": "field_image",
            "src": Blockly.mainWorkspace.options.pathToMedia + "repeat.svg",
            "width": 24,
            "height": 24,
            "alt": "*",
            "flip_rtl": true
          }
        ],
        "category": Blockly.Categories.control,
        "extensions": ["colours_control", "shape_statement"]
      });
    }
docs: Block to repeat until a condition becomes true.
  @this Blockly.Block