Make dumbdbm merely "dumb", rather than "terminally broken". Without this
patch, it's almost impossible to use dumbdbm _without_ causing horrible
datalossage. With this patch, dumbdbm passes my own horrible torture test,
as well as the roundup test suite.
dumbdbm really could do with a smidgin of a rewrite or two, but that's not
suitable for the release21-maint branch.
There is a silly bug in the fall-back dumbdbm.py database package in
the Python 1.5.2 standard distro. This bug causes any changes to an
existing item to generate a new key, even when the key already
exists. After many updates, the .dir file used by dumbdbm grows to
a huge size, and can cause filesystem problems.