t/cgi.t: show stderr on failures

This helped me diagnose an error I would've introduced
in the next commit.

1 files changed, 1 insertions, 1 deletions

diff --git a/t/cgi.t b/t/cgi.t
index 366d6594..96c627c3 100644
--- a/t/cgi.t
+++ b/t/cgi.t
@@ -158,7 +158,7 @@ sub cgi_run {
         my ($in, $out, $err) = ("", "", "");
         my $rdr = { 0 => \$in, 1 => \$out, 2 => \$err };
         run_script(['.cgi'], \%env, $rdr);
-        die "unexpected error: \$?=$?" if $?;
+        die "unexpected error: \$?=$? ($err)" if $?;
         my ($head, $body) = split(/\r\n\r\n/, $out, 2);
         { head => $head, body => $body, err => $err }
 }