Prefer setdefault to hasattr/setattr

setuptools/dist.py

@@ -267,8 +267,7 @@ class Distribution(_Distribution):
         if attrs and 'setup_requires' in attrs:
             self.fetch_build_eggs(attrs['setup_requires'])
         for ep in pkg_resources.iter_entry_points('distutils.setup_keywords'):
-            if not hasattr(self,ep.name):
-                setattr(self,ep.name,None)
+            vars(self).setdefault(ep.name, None)
         _Distribution.__init__(self,attrs)
         if isinstance(self.metadata.version, numbers.Number):
             # Some people apparently take "version number" too literally :)