# File lib/rubygems/old_format.rb, line 36
    def self.from_file_by_path(file_path)
      unless File.exist?(file_path)
        raise Gem::Exception, "Cannot load gem file [#{file_path}]"
      end
      File.open(file_path, 'rb') do |file|
        from_io(file, file_path)
      end
    end