One problem with hexdigest is that it's longer and the column was
created as binary(16). We don't have a mechanism to run migrations on
this table, so we use UNHEX in SQL to have the equivalent as digest()
from hexdigest()
Co-authored-by: Jérome Perrin <jerome@nexedi.com>

Jérome: slightly adjusted manually to just use range where it does not
make a significant difference (for example in test)

also str representation of unicode character is different.