Normalizes default layer name.

    * **value** must normalize as layer name with
      :func:`normalizeLayerName`.
    * **value** must be a layer in **font**.
    * Returned value will be an unencoded ``unicode`` string.

def normalizeDefaultLayerName(value, font):
    """
    Normalizes default layer name.

    * **value** must normalize as layer name with
      :func:`normalizeLayerName`.
    * **value** must be a layer in **font**.
    * Returned value will be an unencoded ``unicode`` string.
    """
    value = normalizeLayerName(value)
    if value not in font.layerOrder:
        raise ValueError("No layer with the name '%s' exists." % value)
    return unicode(value)