Use yaml.safe_load

yaml.load is deprecated from PyYAML 5.1:
  https://github.com/yaml/pyyaml/wiki/PyYAML-yaml.load(input)-Deprecation

Author: khinsen

article.py

@@ -167,7 +167,7 @@ def __init__(self, data):
 
 
     def parse(self, data):
-        document = yaml.load(data)
+        document = yaml.safe_load(data)
 
         self.title = document.get("title", "")
         self.abstract = document.get("abstract","") or ""