The 2**16 in the error message is wrong.  Maybe the error message should
be something like:

"Attempt to create array of size larger than maxsize failed to raise
MemoryError."

A bit verbose, but more accurate.

There's another error in that patch, too.  The line:

b * maxsize//3 + 1

should be

b * (maxsize//3 + 1)

(I was mistakenly reading the '*' as '*=', as in the first test.)