Flake8 cleanup.

It appears that the latest version of flake8 caught a couple more things.

Author: waylan

mkdocs/config/config_options.py

@@ -487,8 +487,8 @@ def run_validation(self, value):
         if len(value) == 0:
             return
 
-        config_types = {type(l) for l in value}
-        if config_types.issubset({str, dict, str}):
+        config_types = {type(item) for item in value}
+        if config_types.issubset({str, dict}):
             return value
 
         raise ValidationError("Invalid pages config. {} {}".format(

mkdocs/plugins.py

@@ -68,7 +68,7 @@ def _register_event(self, event_name, method):
     def __setitem__(self, key, value, **kwargs):
         if not isinstance(value, BasePlugin):
             raise TypeError(
-                '{0}.{1} only accepts values which are instances of {3}.{4} '
+                '{0}.{1} only accepts values which are instances of {2}.{3} '
                 'sublcasses'.format(self.__module__, self.__name__,
                                     BasePlugin.__module__, BasePlugin.__name__))
         super().__setitem__(key, value, **kwargs)