Exit only if authentication explicitly failed (#1806)

It could happen that one of etcd servers is not accessible on Patroni start.
In this case Patroni was trying to perform authentication and exiting, while it should exit only if Etcd explicitly responded with the `AuthFailed` error.

Close https://github.com/zalando/patroni/issues/1805

patroni/dcs/etcd3.py

@@ -98,6 +98,10 @@ class UserEmpty(InvalidArgument):
     error = "etcdserver: user name is empty"
 
 
+class AuthFailed(InvalidArgument):
+    error = "etcdserver: authentication failed, invalid user ID or password"
+
+
 class PermissionDenied(Etcd3ClientError):
     code = GRPCCode.PermissionDenied
     error = "etcdserver: permission denied"
@@ -186,7 +190,7 @@ class Etcd3Client(AbstractEtcdClientWithFailover):
 
         try:
             self.authenticate()
-        except Exception as e:
+        except AuthFailed as e:
             logger.fatal('Etcd3 authentication failed: %r', e)
             sys.exit(1)
 

tests/test_etcd3.py

@@ -5,7 +5,7 @@ import urllib3
 
 from mock import Mock, patch
 from patroni.dcs.etcd3 import PatroniEtcd3Client, Cluster, Etcd3, Etcd3Error, Etcd3ClientError, RetryFailedError,\
-        InvalidAuthToken, Unavailable, Unknown, UnsupportedEtcdVersion, UserEmpty, base64_encode
+        InvalidAuthToken, Unavailable, Unknown, UnsupportedEtcdVersion, UserEmpty, AuthFailed, base64_encode
 from threading import Thread
 
 from . import SleepException, MockResponse
@@ -90,7 +90,7 @@ class TestKVCache(BaseTestEtcd3):
 
 class TestPatroniEtcd3Client(BaseTestEtcd3):
 
-    @patch('patroni.dcs.etcd3.Etcd3Client.authenticate', Mock(side_effect=Exception))
+    @patch('patroni.dcs.etcd3.Etcd3Client.authenticate', Mock(side_effect=AuthFailed))
     def test__init__(self):
         self.assertRaises(SystemExit, self.setUp)