Call Paste's FileApp (a WSGI application) to serve the file
        at the specified path

def _serve_file(self, path):
        """Call Paste's FileApp (a WSGI application) to serve the file
        at the specified path
        """
        static = PkgResourcesParser('pylons', 'pylons')
        request.environ['PATH_INFO'] = '/%s' % path
        return static(request.environ, self.start_response)