Connects to the cloud web services. If this is the first
        authentication, a web browser will be started to authenticate
        against google and provide access to elasticluster.

        :return: A Resource object with methods for interacting with the
                 service.

def _connect(self):
        """Connects to the cloud web services. If this is the first
        authentication, a web browser will be started to authenticate
        against google and provide access to elasticluster.

        :return: A Resource object with methods for interacting with the
                 service.
        """
        # check for existing connection
        with GoogleCloudProvider.__gce_lock:
            if self._gce:
                return self._gce

            flow = OAuth2WebServerFlow(self._client_id, self._client_secret,
                                       GCE_SCOPE)
            # The `Storage` object holds the credentials that your
            # application needs to authorize access to the user's
            # data. The name of the credentials file is provided. If the
            # file does not exist, it is created. This object can only
            # hold credentials for a single user. It stores the access
            # priviledges for the application, so a user only has to grant
            # access through the web interface once.
            storage_path = os.path.join(self._storage_path,
                                        self._client_id + '.oauth.dat')
            storage = Storage(storage_path)

            credentials = storage.get()
            if credentials is None or credentials.invalid:
                args = argparser.parse_args([])
                args.noauth_local_webserver = self._noauth_local_webserver
                # try to start a browser to have the user authenticate with Google
                # TODO: what kind of exception is raised if the browser
                #       cannot be started?
                try:
                    credentials = run_flow(flow, storage, flags=args)
                except:
                    import sys
                    print "Unexpected error:", sys.exc_info()[0]
                    raise

            http = httplib2.Http()
            self._auth_http = credentials.authorize(http)

            self._gce = build(GCE_API_NAME, GCE_API_VERSION, http=http)

            return self._gce