[dataformat] Read and decode from file before loading json

beat/backend/python/dataformat.py

@@ -168,7 +168,7 @@ class DataFormat(object):
                 return
 
             with open(json_path, 'rb') as f:
-                self.data = simplejson.load(f)
+                self.data = simplejson.loads(f.read().decode('utf-8'))
 
         dataformat_cache[self._name] = self #registers itself into the cache