due to the coarseness of time.time() on Windows.  It looks like an
attempt was made before to fix this, and also removed a wrong comment
explaining that fix.  .pack() used to be documented incorrectly, saying
that stuff before the pack time was packed away.  It's actually the case
that stuff before *or equal to* the pack time is packed away, and that's
a crucial distinction on Windows because time.time() often (usually,
in fact) returns the same value on two successive calls.  The earlier
fix attempt tried to separate observed time.time() values, but did so
before the pack().  That's usually appropriate, but in this test we
really need to make sure that object revisions *after* the pack() get
timestamps distinct from the pack time (else they'll get packed away,
and the test isn't expecting that).