def to_s
      sanitized_url = sanitize_url(generated_permalink || generated_url)
      if sanitized_url.include?(":")
        raise Bunto::Errors::InvalidURLError,
          "The URL #{sanitized_url} is invalid because it contains a colon."
      else
        sanitized_url
      end
    end
def to_s
      sanitized_url = sanitize_url(generated_permalink || generated_url)
      if sanitized_url.include?(":")
        raise Bunto::Errors::InvalidURLError,
          "The URL #{sanitized_url} is invalid because it contains a colon."
      else
        sanitized_url
      end
    end
options - One of :permalink or :template must be supplied.
           :template     - The String used as template for URL generation,
                           for example "/:path/:basename:output_ext", where
                           a placeholder is prefixed with a colon.
           :placeholders - A hash containing the placeholders which will be
                           replaced when used inside the template. E.g.
                           { "year" => Time.now.strftime("%Y") } would replace
                           the placeholder ":year" with the current year.
           :permalink    - If supplied, no URL will be generated from the
                           template. Instead, the given permalink will be
                           used as URL.
 The generated relative URL of the resource

 Returns the String URL
 Raises a Bunto::Errors::InvalidURLError if the relative URL contains a colon