autopkgtest regression blocking mysql-8.0

[Lucas Kanashiro]

libdbd-mariadb-perl/1.11-3ubuntu2 regressed in all architectures when tests are executed with mysql-8.0/8.0.20-0ubuntu1, blocking mysql-8.0 migration. For instance this is the amd64 test log:

https://objectstorage.prodstack4-5.canonical.com/v1/AUTH_77e2ada1e7a84929a74ba3b87153c0ac/autopkgtest-groovy/groovy/amd64/libd/libdbd-mariadb-perl/20200507_133547_a903f@/log.gz

The test file which is failing is:

t/13disconnect.t (Wstat: 139 Tests: 15 Failed: 0)
  Non-zero wait status: 139
  Parse errors: Bad plan. You planned 17 tests but ran 15.

Two tests in this file are failing. After disconnecting to the MariaDB server the two connections created previously are still active (the last two 'ok' commands are failing):

ok my $dbh4 = DBI->connect($test_dsn, $test_user, $test_password, { RaiseError => 1, PrintError => 0 });
ok our $dbh5 = DBI->connect($test_dsn, $test_user, $test_password, { RaiseError => 1, PrintError => 0 });

ok $dbh4->{Active};
ok $dbh5->{Active};

# install a handler so that a warning about unfreed resources gets caught
$SIG{__WARN__} = sub { die @_ };

DBI->disconnect_all();

ok !$dbh4->{Active};
ok !$dbh5->{Active};