def format(filename=nil, line=nil)
      out = ""
      if filename
        out = Util::OS.windows? ? filename.gsub('/', '\\') : filename
        if line
          out += ":#{line}:"
        end
      end
      paint(:magenta, out)
    end
def format(filename=nil, line=nil)
      out = ""
      if filename
        out = Util::OS.windows? ? filename.gsub('/', '\\') : filename
        if line
          out += ":#{line}:"
        end
      end
      paint(:magenta, out)
    end
Formats filename and line number for output