livemedia-creator: Fix up fake yum object for DNF change

pylorax unconditionally calls reset() on the dbo, so provide an empty
method to keep it happy.

The lmc dbo is minimal because it is only used for creating the iso, not
anything related to package installation.

src/sbin/livemedia-creator

@@ -308,6 +308,21 @@ class IsoMountpoint(object):
                 return
 
 
+class FakeDNF(object):
+    """
+    A minimal DNF object suitable for passing to RuntimeBuilder
+
+    lmc uses RuntimeBuilder to run the arch specific iso creation
+    templates, so the the installroot config value is the important part of
+    this. Everything else should be a nop.
+    """
+    def __init__(self, conf):
+        self.conf = conf
+
+    def reset(self):
+        pass
+
+
 class VirtualInstall(object):
     """
     Run virt-install using an iso and a kickstart
@@ -550,8 +565,8 @@ def make_runtime(opts, mount_dir, work_dir):
     """
     kernel_arch = get_arch(mount_dir)
 
-    # Fake yum object
-    fake_yum = DataHolder(conf=DataHolder(installroot=mount_dir))
+    # Fake dnf  object
+    fake_dbo = FakeDNF(conf=DataHolder(installroot=mount_dir))
     # Fake arch with only basearch set
     arch = ArchData(kernel_arch)
     # TODO: Need to get release info from someplace...
@@ -562,7 +577,7 @@ def make_runtime(opts, mount_dir, work_dir):
     # symlink mount_dir/images to work_dir/images so we don't run out of space
     os.makedirs(joinpaths(work_dir, "images"))
 
-    rb = RuntimeBuilder(product, arch, fake_yum)
+    rb = RuntimeBuilder(product, arch, fake_dbo)
     log.info("Creating runtime")
     rb.create_runtime(joinpaths(work_dir, RUNTIME), size=None)