The tests which are failing were in introduced in #5712. Those were not
included in #5710 which updated `picojson` that resulted in the
different lines being reported in the error messages.
I also added some checks to `ScopeFile` which will indicate that a
temporary file already exists highlighting multi-threading issues and
leftover files from previously aborted testruns. I ran into his while
looking into these failing tests
I want to use Suppressions class also in GUI. And that is easier
to do when it is not internal class of Settings class. And in
general is it more natural that Settings class only contains list
of suppressions and implementation is separate.