Next version is actually a metapackage depending on:
  persistent 4.0
  BTrees 4.0
  ZODB 4.0
  ZEO 4.0

Note that version '123dev' is considered lower than '123'

Update (only) user.

This fixes a bug causing a crash during tpc_finish phase when a storage
involved in a transaction does not receive any object, but receives at
least one CheckCurrentSerial request: no transaction was registered, and
storage would fail to lock transaction when requested by master during
tpc_finish phase.

In particular, do not flush all debug logs still in memory