depsolve: filter out conflicting provider. BZ 1480065

When there are multiple providers available for a requirement, yum would
happily pick the one that the requiring package also has a "Conflicts:"
on (via another virtual provide), failing to resolve the transaction.

Example:
- foo requires bar and conflicts my-bar
- bax provides bar
- bay provides bar, my-bar

Yum might decide to pick bay, only to fail due to the conflict with foo
later in the process.

This commit fixes that by dropping such a provider from the candidate
list when depsolving.

Author: dmnks

yum/depsolve.py

@@ -1556,6 +1556,13 @@ def _pkg2prov_version(pkg, provname):
                 continue
             unique_nevra_pkgs[pkg.pkgtup] = pkg
         pkgs = unique_nevra_pkgs.values()
+
+        # Do a conflict filtering; get rid of those pkgs that reqpo conflicts
+        # with
+        if reqpo is not None:
+            pkgs = [pkg for pkg in pkgs
+                        if not any(pkg.checkPrco('provides', conflict)
+                                   for conflict in reqpo.conflicts)]
 
         pkgresults = {}