[test/querier] use the new connection api (part 1/3) In devtools/repotest, we provide a simple `.qexecute` with autocommit, and we use it (where possible) in unittest_querier. Note that the .session object is a real session, not the magic property found in CubicWebTC test classes.

if not rql('CWConstraintType X WHERE X name "RQLUniqueConstraint"',
           ask_confirm=False):
    rql('INSERT CWConstraintType X: X name "RQLUniqueConstraint"',
        ask_confirm=False)