test: Make pylint happier.

caucase/test.py

@@ -1176,13 +1176,16 @@ class CaucaseTest(unittest.TestCase):
       Mock CAU.
       """
       digest_list = ['sha256']
-      def getCACertificateList(self):
+
+      @staticmethod
+      def getCACertificateList():
         """
         Return cau ca list.
         """
         return cau_list
 
-      def getCertificateRevocationList(self):
+      @staticmethod
+      def getCertificateRevocationList():
         """
         Return cau crl.
         """