Unable create partition by trigger 1) I have table

CREATE TABLE tor
(
  events_date timestamp without time zone NOT NULL,
  message text
  CONSTRAINT tor_pkey PRIMARY KEY (events_date, message)
)PARTITION BY RANGE (events_date);


2) There is a default partition where the data gets, if there is no partition where you can put it

CREATE TABLE tor_part_default partition OF tor default;


3) There is a trigger on an INSERT to tor_part_default:

CREATE OR REPLACE FUNCTION create_next_part()
    RETURNS trigger
    LANGUAGE 'plpgsql'
    COST 100
    VOLATILE NOT LEAKPROOF
AS $BODY$
DECLARE
    partname VARCHAR(11);
    startdate VARCHAR(10);
    enddate VARCHAR(10);
BEGIN
    partname = 'tor_'||to_char(NEW.events_date, 'YYYYMM');
    startdate = to_char(NEW.events_date, 'YYYY-MM-01');
    enddate = to_char(TO_DATE(startdate,'YYYY-MM-DD') + interval '1 month','YYYY-MM-DD');
    RAISE NOTICE '    Start date: %',startdate;
    RAISE NOTICE '      End date: %',enddate;
    IF NOT EXISTS (SELECT 1 FROM   information_schema.tables WHERE  table_name = partname) 
    THEN
        RAISE NOTICE 'Partition created: %',partname;
        EXECUTE 'CREATE TABLE '||partname||' partition OF tor FOR VALUES FROM ('''||startdate||''') TO ('''||enddate||''')';
        EXECUTE 'INSERT INTO '||partname||' VALUES(NEW.*)';
    END IF;
    RETURN NEW;
    END;
    $BODY$;

CREATE TRIGGER tor_create_next_part
    BEFORE INSERT
    ON tor_part_default
    FOR EACH ROW
    EXECUTE PROCEDURE create_next_part();


When I try to insert data, as a result I get an error:

ERROR:  cannot CREATE TABLE .. PARTITION OF "tor" because it is being used by active queries in this session
CONTEXT:  SQL statement "CREATE TABLE tor_201606 partition OF tor FOR VALUES FROM ('2016-06-01') TO ('2016-07-01')"
PL/pgSQL function create_next_part() line 16 at EXECUTE


What am I doing wrong or is there another way to create partitions automatically?
It's not possible to modify table via trigger. 

So I have 2 options:


Add partition via cron.
Add partition via code (check default partition).