Comment 5 for bug 651524

The difference between -i and -U comes from the fact that with -U, the rpmdb has already been opened (well, created) whereas with -i it's not. With -i, it also depends on whether the package is signed or not (or whether signature checking is disabled) - signature checking also opens (and creates in this case) the rpmdb early, creating the directory where the lock will be placed. The --initdb case is more straightforward: the directory is always missing, causing failure.

devel_ack, the fix is a trivial one-liner patch.