Set decoding of path to unicode to raise an exception if non-utf8

Letting it pass would just cause an error later on (no such file found)
so it's better to catch it here and know that we have users dealing with
non-utf8 pathnames than to have to track it down from later on.

lib/ansible/inventory/__init__.py

@@ -735,11 +735,11 @@ class Inventory(object):
 
             if group and host is None:
                 # load vars in dir/group_vars/name_of_group
-                base_path = os.path.realpath(os.path.join(to_unicode(basedir), "group_vars/%s" % group.name))
+                base_path = os.path.realpath(os.path.join(to_unicode(basedir, errors='strict'), "group_vars/%s" % group.name))
                 results = combine_vars(results, self._variable_manager.add_group_vars_file(base_path, self._loader))
             elif host and group is None:
                 # same for hostvars in dir/host_vars/name_of_host
-                base_path = os.path.realpath(os.path.join(to_unicode(basedir), "host_vars/%s" % host.name))
+                base_path = os.path.realpath(os.path.join(to_unicode(basedir, errors='strict'), "host_vars/%s" % host.name))
                 results = combine_vars(results, self._variable_manager.add_host_vars_file(base_path, self._loader))
 
         # all done, results is a dictionary of variables for this particular host.