Bug 1250944 - 001compile.t doesn't set error mode, so errors exit the test suite

Bugzilla/Error.pm

@@ -25,7 +25,6 @@ use Date::Format;
 
 sub _throw_error {
     my ($name, $error, $vars) = @_;
-    my $dbh = Bugzilla->dbh;
     my $cache = Bugzilla->request_cache;
     $vars ||= {};
 

t/001compile.t

@@ -25,6 +25,7 @@ BEGIN {
     use_ok('Bugzilla::Install::Requirements');
     use_ok('Bugzilla');
 }
+Bugzilla->usage_mode(USAGE_MODE_TEST);
 
 sub compile_file {
     my ($file) = @_;