Use unsigned version format. This way can use one additional bit, and when encountering invalid revlogs with the first bit set don't produce python warnings or strange error messages.

#!/bin/sh

mkdir t
cd t
hg init
echo a > a
hg add a
hg commit -m "test" -d "1000000 0"
hg verify
hg parents
hg status
hg rollback
hg verify
hg parents
hg status