Stop using deprecated API

fixes kubernetes-client#2169

Author: arcivanov

kubernetes/client/exceptions.py

@@ -88,7 +88,7 @@ def __init__(self, status=None, reason=None, http_resp=None):
             self.status = http_resp.status
             self.reason = http_resp.reason
             self.body = http_resp.data
-            self.headers = http_resp.getheaders()
+            self.headers = http_resp.headers
         else:
             self.status = status
             self.reason = reason