code: @Nonnull
    @Nonempty
    public static String getAsCSSURL (@Nonnull final String sURL, final boolean bForceQuoteURL)
    {
      ValueEnforcer.notNull (sURL, "URL");
  
      final StringBuilder aSB = new StringBuilder (CCSSValue.PREFIX_URL_OPEN);
      final boolean bAreQuotesRequired = bForceQuoteURL || isCSSURLRequiringQuotes (sURL);
      if (bAreQuotesRequired)
      {
        // Determine the best quote char to use - default to '\'' for backwards
        // compatibility
        final int nIndexSingleQuote = sURL.indexOf ('\'');
        final int nIndexDoubleQuote = sURL.indexOf ('"');
        final char cQuote = nIndexSingleQuote >= 0 && nIndexDoubleQuote < 0 ? '"' : '\'';
        // Append the quoted and escaped URL
        aSB.append (cQuote).append (getEscapedCSSURL (sURL, cQuote)).append (cQuote);
      }
      else
      {
        // No quotes needed
        aSB.append (sURL);
      }
      return aSB.append (CCSSValue.SUFFIX_URL_CLOSE).toString ();
    }
docs: Surround the passed URL with the CSS "url(...)". When the passed URL
  contains characters that require quoting, quotes are automatically added!
  
  @param sURL
  URL to be wrapped. May not be <code>null</code> but maybe empty.
  @param bForceQuoteURL
  if <code>true</code> single quotes are added around the URL
  @return <code>url(<i>sURL</i>)</code> or <code>url('<i>sURL</i>')</code>