    # File lib/rubygems/source_index.rb, line 81
        def load_specification(file_name)
          begin
            spec_code = File.read(file_name).untaint
            gemspec = eval spec_code, binding, file_name
            if gemspec.is_a?(Gem::Specification)
              gemspec.loaded_from = file_name
              return gemspec
            end
            alert_warning "File '#{file_name}' does not evaluate to a gem specification"
          rescue SignalException, SystemExit
            raise
          rescue SyntaxError => e
            alert_warning e
            alert_warning spec_code
          rescue Exception => e
            alert_warning(e.inspect.to_s + "\n" + spec_code)
            alert_warning "Invalid .gemspec format in '#{file_name}'"
          end
          return nil
        end