Update depsolving with suggestions from dnf (#1636239)

The previous method worked, but wasn't exactly idiomatic. This is more
correct, and appears to work the same (templates depsolve, version globs
work, multiple repos work).

Note that this does use a private dnf attribute ._goal, but the word is
that this is going to become a public api soon, so yes it is there on
purpose.

Resolves: rhbz#1638683

src/pylorax/api/projects.py

@@ -207,23 +207,25 @@ def _depsolve(dbo, projects, groups):
             install_errors.append(("Group %s" % (name), str(e)))
 
     for name, version in projects:
-        try:
-            if not version:
-                version = "*"
-            pkgs = [pkg for pkg in dnf.subject.Subject(name).get_best_query(dbo.sack).filter(version__glob=version, latest=True)]
-            if not pkgs:
-                install_errors.append(("%s-%s" % (name, version), "No match"))
-                continue
+        # Find the best package matching the name + version glob
+        # dnf can return multiple packages if it is in more than 1 repository
+        query = dbo.sack.query().filterm(provides__glob=name)
+        if version:
+            query.filterm(version__glob=version)
 
-            for p in pkgs:
-                dbo.package_install(p)
-        except dnf.exceptions.MarkingError as e:
-            install_errors.append(("%s-%s" % (name, version), str(e)))
+        query.filterm(latest=1)
+        if not query:
+            install_errors.append(("%s-%s" % (name, version), "No match"))
+            continue
+        sltr = dnf.selector.Selector(dbo.sack).set(pkg=query)
+
+        # NOTE: dnf says in near future there will be a "goal" attribute of Base class
+        #       so yes, we're using a 'private' attribute here on purpose and with permission.
+        dbo._goal.install(select=sltr, optional=False)
 
     if install_errors:
         raise ProjectsError("The following package(s) had problems: %s" % ",".join(["%s (%s)" % (pattern, err) for pattern, err in install_errors]))
 
-
 def projects_depsolve(dbo, projects, groups):
     """Return the dependencies for a list of projects