A. default (autobegin)
  acquired: True, holder state: idle in transaction
  t=1s other process gets lock: False
  t=5s other process gets lock: True
  holder's next query fails: OperationalError
B. AUTOCOMMIT
  acquired: True, holder state: idle
  t=1s other process gets lock: False
  t=5s other process gets lock: False
  holder: alive
C. commit right after acquire
  acquired: True, holder state: idle
  t=1s other process gets lock: False
  t=5s other process gets lock: False
  holder: alive
D. commit, then one more query
  acquired: True, holder state: idle in transaction
  t=1s other process gets lock: False
  t=5s other process gets lock: True
  holder's next query fails: OperationalError
E. AUTOCOMMIT, with idle_session_timeout
  acquired: True, holder state: idle
  t=1s other process gets lock: False
  t=5s other process gets lock: True
  holder's next query fails: OperationalError