Fix plugin loading at startup

                def plugins_install():

                    for p in to_load:

                        try:

                            self.plugin_install(self.main.rpc.rpc_con, None, p)

                            self.plugin_install(self.main.rpc_con.rpc, None, p)

                        except Exception:

                            logger.exception('Error while loading plugin %s', p)

                        else:

    @pass_connection

    def plugin_install(self, conn, sha1, name):

        """

        :param conn: RPC connection

        :param sha1: sha1 string or None (get the latest)

        :param name: plugin name

        """

        # check if plugin is not already loaded and upgrade it if the sha1 hash

        # has changed:

        if name in self.plugins:

        # get plugin from server:

        sha1_get, content = conn.call('plugin_get', name)

        if sha1 != sha1_get:

        if sha1 is not None and sha1 != sha1_get:

            raise RuntimeError('Requested sha1 is not available on the server')

        # load the plugin: