DuplicateRule error creates index out of bound stacktrace
Motivation
----------
```
File "/usr/lib/python2.7/site-packages/rucio/web/rest/rule.py", line 271, in POST
raise generate_http_error(409, 'DuplicateRule', error.args[0])
IndexError: tuple index out of range
```
[0] needs to be removed.

diff --git a/lib/rucio/web/rest/webpy/v1/rule.py b/lib/rucio/web/rest/webpy/v1/rule.py
index 1f261ea78..173011322 100755
--- a/lib/rucio/web/rest/webpy/v1/rule.py
+++ b/lib/rucio/web/rest/webpy/v1/rule.py
@@ -1,15 +1,25 @@
-'''
-  Copyright European Organization for Nuclear Research (CERN)
+# Copyright 2012-2018 CERN for the benefit of the ATLAS collaboration.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+# Authors:
+# - Vincent Garonne <vgaronne@gmail.com>, 2012-2017
+# - Mario Lassnig <mario.lassnig@cern.ch>, 2013-2018
+# - Thomas Beermann <thomas.beermann@cern.ch>, 2013-2018
+# - Martin Barisits <martin.barisits@cern.ch>, 2013-2017
+# - Cedric Serfon <cedric.serfon@cern.ch>, 2014-2017
+# - Joaquin Bogado <jbogado@linti.unlp.edu.ar>, 2018
 
-  Licensed under the Apache License, Version 2.0 (the "License");
-  You may not use this file except in compliance with the License.
-  You may obtain a copy of the License at http://www.apache.org/licenses/LICENSE-2.0
-
-  Authors:
-  - Vincent Garonne, <vincent.garonne@cern.ch>, 2012-2017
-  - Martin Barisits, <martin.barisits@cern.ch>, 2013-2017
-  - Cedric Serfon, <cedric.serfon@cern.ch>, 2015, 2017
-'''
 
 from logging import getLogger, StreamHandler, DEBUG
 from json import dumps, loads
@@ -268,7 +278,7 @@ class AllRule:
         except InvalidReplicationRule as error:
             raise generate_http_error(409, 'InvalidReplicationRule', error.args[0][0])
         except DuplicateRule as error:
-            raise generate_http_error(409, 'DuplicateRule', error.args[0])
+            raise generate_http_error(409, 'DuplicateRule', error.args)
         except InsufficientTargetRSEs as error:
             raise generate_http_error(409, 'InsufficientTargetRSEs', error.args[0][0])
         except InsufficientAccountLimit as error:
['lib/rucio/web/rest/webpy/v1/rule.py']