Parsed test spec with 2 sessions

starting permutation: s1-insert-1 s2-insert s1-commit s2-commit
create_distributed_table
---------------------------------------------------------------------

(1 row)

step s1-insert-1:
  BEGIN;
  INSERT INTO test_locking (a) VALUES (1);

step s2-insert:
  BEGIN;
  INSERT INTO test_locking (a) VALUES (1);
 <waiting ...>
step s1-commit: 
  COMMIT;

step s2-insert: <... completed>
ERROR:  duplicate key value violates unique constraint "test_locking_a_key_1400001"
step s2-commit:
  COMMIT;

