[common][serializers] Fix key search in dictionaries

beat/web/common/serializers.py

@@ -330,7 +330,7 @@ class ContributionCreationSerializer(serializers.ModelSerializer):
         name = self.Meta.model.sanitize_name(data['name'])
         data['name'] = name
 
-        if data.has_key('previous_version'):
+        if 'previous_version' in data:
             if self.Meta.beat_core_class is not None:
                 previous_version_id = self.Meta.beat_core_class.Storage(settings.PREFIX,
                                                                         data['previous_version'])
@@ -345,7 +345,7 @@ class ContributionCreationSerializer(serializers.ModelSerializer):
         else:
             previous_version_id = None
 
-        if data.has_key('fork_of'):
+        if 'fork_of' in data:
             if self.Meta.beat_core_class is not None:
                 fork_of_id = self.Meta.beat_core_class.Storage(settings.PREFIX,
                                                                data['fork_of'])