mark spacewalk.releng namespace as obsolete

I done s/spacewalk.releng./tito./ in spacewalk.git, but it may reside in some (private) branches.
So let keep it for little bit more releases, but print warnings.

src/tito/common.py

@@ -543,6 +543,7 @@ def normalize_class_name(name):
     """
     look_for = "spacewalk.releng."
     if name.startswith(look_for):
+        sys.stderr.write("Warning: spacewalk.releng.* namespace in tito.props is obsolete. Use tito.* instead.\n")
         name = "%s%s" % ("tito.", name[len(look_for):])
     return name
 

tito.props.5.asciidoc

@@ -177,7 +177,7 @@ EXAMPLE
 -------
  [globalconfig]
  default_builder = tito.builder.Builder
- default_tagger = spacewalk.releng.tagger.VersionTagger
+ default_tagger = tito.tagger.VersionTagger
 
  [koji]
  autobuild_tags = dist-5E-sw-1.2-candidate dist-f12-sw-1.2-candidate dist-f13-sw-1.2-candidate