Add missing variable declaration

beat/backend/python/algorithm.py

@@ -270,6 +270,7 @@ class Algorithm(object):
     self.dataformats = {}
     self.libraries = {}
     self.groups = []
+    self.errors = []
 
     dataformat_cache = dataformat_cache if dataformat_cache is not None else {}
     library_cache = library_cache if library_cache is not None else {}

beat/backend/python/library.py

@@ -117,7 +117,7 @@ class Library(object):
     self._name = None
     self.storage = None
     self.prefix = prefix
-
+    self.errors = []
     self.libraries = {}
 
     library_cache = library_cache if library_cache is not None else {}