Use dnf backend for repoclosure on PY3

When yum is not available, it makes no sense to offer it as an option.

Signed-off-by: Lubomír Sedlář <lsedlar@redhat.com>

doc/configuration.rst

@@ -172,7 +172,7 @@ Options
     (*str*) -- Select which tool should be used to run repoclosure over created
     repositories. By default ``yum`` is used, but you can switch to ``dnf``.
     Please note that when ``dnf`` is used, the build dependencies check is
-    skipped.
+    skipped. On Python 3, only ``dnf`` backend is available.
 
 **compose_type**
     (*str*) -- Allows to set default compose type. Type set via a command-line

pungi/checks.py

@@ -614,8 +614,9 @@ def make_schema():
             }),
             "repoclosure_backend": {
                 "type": "string",
-                "default": "yum",
-                "enum": ["yum", "dnf"],
+                # Gather and repoclosure both have the same backends: yum + dnf
+                "default": _get_default_gather_backend(),
+                "enum": _get_gather_backends(),
             },
 
             "old_composes_per_release_type": {

tests/test_config.py

@@ -427,9 +427,10 @@ class RepoclosureTestCase(ConfigTestCase):
             repoclosure_backend='fnd',  # Intentionally with a typo
         )
 
+        options = ['yum', 'dnf'] if six.PY2 else ['dnf']
         self.assertValidation(
             cfg,
-            ["Failed validation in repoclosure_backend: 'fnd' is not one of ['yum', 'dnf']"])
+            ["Failed validation in repoclosure_backend: 'fnd' is not one of %s" % options])
 
 
 if __name__ == '__main__':

tests/test_test_phase.py

@@ -192,7 +192,9 @@ class TestRepoclosure(PungiTestCase):
     @mock.patch('pungi.wrappers.repoclosure.get_repoclosure_cmd')
     @mock.patch('pungi.phases.test.run')
     def test_repoclosure_default_backend(self, mock_run, mock_grc):
+        with mock.patch('six.PY2', new=True):
             compose = DummyCompose(self.topdir, {})
+
         test_phase.run_repoclosure(compose)
 
         self.assertItemsEqual(