optional_plugins: Decode tree-representation in yaml_to_mux

The 'tree.tree_view' reports bytes, but the 'to_str' method is supposed
to return text. To avoid mix-matching bytes and strings let's always
decode.

It's not really necessary to differentiate between ascii/utf8 as those
are the only encodings and ascii is a subset of utf8.
Signed-off-by: NLukáš Doktor <ldoktor@redhat.com>

optional_plugins/runner_remote/avocado_runner_remote/__init__.py

@@ -458,7 +458,8 @@ class RemoteTestRunner(TestRunner):
         try:
             json_result = self._parse_json_response(result.stdout)
         except:
-            stacktrace.log_exc_info(sys.exc_info(), logger='avocado.debug')
+            stacktrace.log_exc_info(sys.exc_info(),
+                                    logger='avocado.app.debug')
             raise exceptions.JobError(result.stdout)
 
         for t_dict in json_result['tests']:

optional_plugins/varianter_yaml_to_mux/avocado_varianter_yaml_to_mux/mux.py

@@ -211,7 +211,8 @@ class MuxPlugin(object):
             # summary == 0 means disable, but in plugin it's brief
             tree_repr = tree.tree_view(self.root, verbose=summary - 1,
                                        use_utf8=kwargs.get("use_utf8", None))
-            out.append(tree_repr)
+            # ascii is a subset of UTF-8, let's use always UTF-8 to decode here
+            out.append(tree_repr.decode('utf-8'))
             out.append("")
 
         if variants: