Check dnf version before skipping base module conflicts

The base module conflict generation was skipped for local builds
in 6b2e5be93a because libdnf wasn't ported to libmodulemd yet -
that was done in libdnf-0.45, so only warn and skip for versions of
dnf too old to require libdnf-0.45.

(Don't just unconditionally skip check/warning in case someone is
doing local module builds on RHEL 8.)

module_build_service/scheduler/default_modules.py

@@ -9,6 +9,7 @@ import tempfile
 import dnf
 import kobo.rpmlib
 import koji
+import packaging.version
 import six.moves.xmlrpc_client as xmlrpclib
 
 from module_build_service.common import conf, log, models, scm
@@ -216,7 +217,7 @@ def _get_rawhide_version():
         return build_target["build_tag_name"].partition("-build")[0]
 
 
-def handle_collisions_with_base_module_rpms(mmd, arches):
+def handle_collisions_with_base_module_rpms(mmd, arches, force_for_old_dnf=False):
     """
     Find any RPMs in the buildrequired base modules that collide with the buildrequired modules.
 
@@ -226,8 +227,22 @@ def handle_collisions_with_base_module_rpms(mmd, arches):
 
     :param Modulemd.ModuleStream mmd: the modulemd to find the collisions
     :param list arches: the arches to limit the external repo queries to
+    :param bool force_for_old_dnf: add the conflicts even if libdnf can't handle them
     :raise RuntimeError: when a Koji query fails
     """
+    if (not force_for_old_dnf
+            and packaging.version.parse(dnf.VERSION) < packaging.version.parse('4.2.19')):
+        # For local builds, we can't use this code unless libdnf uses libmodulemd2
+        # (done in libdnf-0.45) - we can't check the libdnf version, so use
+        # dnf-4.2.19 (which requires libdnf-0.45) as a proxy.
+        log.warning(
+            "The necessary conflicts could not be generated due to RHBZ#1693683. "
+            "Some RPMs from the base modules (%s) may end up being used over modular RPMs. "
+            "This may result in different behavior than a production build.",
+            ", ".join(conf.base_module_names)
+        )
+        return
+
     log.info("Finding any buildrequired modules that collide with the RPMs in the base modules")
     bm_tags = set()
     non_bm_tags = set()

module_build_service/scheduler/handlers/modules.py

@@ -207,15 +207,8 @@ def init(msg_id, module_build_id, module_build_state):
         # Sets xmd["mbs"]["ursine_rpms"] with RPMs from the buildrequired base modules which
         # conflict with the RPMs from other buildrequired modules. This is done to prefer modular
         # RPMs over base module RPMs even if their NVR is lower.
-        if conf.system in ("koji", "test"):
-            handle_collisions_with_base_module_rpms(mmd, arches)
-        else:
-            log.warning(
-                "The necessary conflicts could not be generated due to RHBZ#1693683. "
-                "Some RPMs from the base modules (%s) may end up being used over modular RPMs. "
-                "This may result in different behavior than a production build.",
-                ", ".join(conf.base_module_names)
-            )
+        handle_collisions_with_base_module_rpms(mmd, arches,
+                                                force_for_old_dnf=conf.system in ("koji", "test"))
 
         mmd = record_filtered_rpms(mmd)
         build.modulemd = mmd_to_str(mmd)

requirements.txt

@@ -13,6 +13,7 @@ koji
 ldap3
 moksha.hub
 munch
+packaging
 prometheus_client
 pygobject
 pyOpenSSL

tests/test_scheduler/test_default_modules.py

@@ -291,7 +291,8 @@ def test_handle_collisions_with_base_module_rpms(mock_grft, mock_get_session):
     }
     mock_grft.side_effect = [bm_rpms, non_bm_rpms]
 
-    default_modules.handle_collisions_with_base_module_rpms(mmd, ["aarch64", "x86_64"])
+    default_modules.handle_collisions_with_base_module_rpms(mmd, ["aarch64", "x86_64"],
+                                                            force_for_old_dnf=True)
 
     mock_get_session.assert_called_once()
     xmd_mbs = mmd.get_xmd()["mbs"]