Merge pull request #203 from allegro/pyyaml_cve_fix

Security fix reported by github

vaas-app/src/vaas/configuration/loader.py

@@ -25,6 +25,6 @@ def get_config_tree(self, config_file):
         config_full_path = self.determine_config_file(config_file)
         if config_full_path:
             with open(config_full_path) as file_stream:
-                return yaml.load(file_stream.read())
+                return yaml.safe_load(file_stream.read())
 
         return {}