Avoid a race condition in crypt testing

Test::Warn fails us here because it only captures the first line of a
multi-line warning.  Opening up the debug log and searching over it
leads to race conditions, as the error we're looking for may not have
been flushed to disk by the time we read it.

Instead, use a simple __WARN__ handler to look for the desired warning.

t/crypt/no-signer-address.t

@@ -2,7 +2,7 @@ use strict;
 use warnings;
 
 use RT::Test::GnuPG
-  tests         => 6,
+  tests         => undef,
   gnupg_options => {
     passphrase    => 'rt-test',
     'trust-model' => 'always',
@@ -19,18 +19,24 @@ my $queue;
     ok !$queue->CorrespondAddress, 'address not set';
 }
 
-use Test::Warn;
-warnings_like {
-    my $ticket = RT::Ticket->new( RT->SystemUser );
-    my ($status, undef, $msg) = $ticket->Create(
-        Queue => $queue->id,
-        Subject => 'test',
-        Requestor => 'root@localhost',
-    );
-    ok $status, "created ticket" or diag "error: $msg";
+# We don't use Test::Warn here, because it apparently only captures up
+# to the first newline -- and the meat of this message is on the fourth
+# line.
+my @warnings;
+local $SIG{__WARN__} = sub {
+    push @warnings, "@_";
+};
+
+my $ticket = RT::Ticket->new( RT->SystemUser );
+my ($status, undef, $msg) = $ticket->Create(
+    Queue => $queue->id,
+    Subject => 'test',
+    Requestor => 'root@localhost',
+);
+ok( $status, "created ticket" ) or diag "error: $msg";
 
-    my $log = RT::Test->file_content([RT::Test->temp_directory, 'rt.debug.log']);
-    like $log, qr{secret key not available}, 'error in the log';
-    unlike $log, qr{Scrip .*? died}m, "scrip didn't die";
-} [qr{gpg: keyring .*? created}];
+is( scalar @warnings, 1, "Got a warning" );
+like( $warnings[0], qr{signing failed: secret key not available},
+    "Found warning of no secret key");
 
+done_testing;