Try to fix test failing on CI

PublishRepo26Test fails to run because something in the CI environment forces
gpg to ask for the user's password. Try to require gpg1 for the test, which
seems to run fine in other environments.

system/t06_publish/repo.py

@@ -682,6 +682,7 @@ class PublishRepo26Test(BaseTest):
     """
     publish repo: sign with passphrase
     """
+    requiresGPG1 = True
     fixtureCmds = [
         "aptly repo create local-repo",
         "aptly repo add local-repo ${files}",