The referenced issue states that it is only applicable to Android < 4.2
(testing confirms the problem on 4.1.2, but not on 4.2.2).
A test was added for the version code, primarily as a finder's aid for a
day when K-9 Mail no longer supports Android < 4.2 and the work-around can
be removed.
The referenced issue also states that it is only necessary to hold a
reference to the first PrivateKey retrieved. (Testing indicates that the
problem is avoided so long at least one reference is always maintained to
a PrivateKey -- it doesn't actually need to be a continuous reference to
the first PrivateKey.)
From my understanding, a normal class loader never unloads a class, so the
static reference can be safely kept privately in KeyChainKeyManager.
ada74db8d5