[PBCKP-231] hotfix for python2

Author: Ivan Lazarev

tests/helpers/ptrack_helpers.py

@@ -1880,7 +1880,7 @@ def __str__(self):
 
 
 class GDBobj:
-    def __init__(self, cmd, env: ProbackupTest, attach=False):
+    def __init__(self, cmd, env, attach=False):
         self.verbose = env.verbose
         self.output = ''