Improve error message for sigv4 and PermanentRedirect errors

The error message now includes a note on specifying the
correct region:

 $ aws s3api list-objects --bucket wrong.region.bucket

 A client error (PermanentRedirect) occurred when calling the ListObjects operation:

 The bucket you are attempting to access must be addressed using the specified
 endpoint. Please send all future requests to this endpoint:
 wrong.region.bucket.s3-ap-southeast-2.amazonaws.com
 You can fix this issue by explicity providing the correct region location
 using the --region argument, the AWS_DEFAULT_REGION environment variable, or
 the region variable in the AWS CLI configuration file.  You can get the
 bucket's location by running "aws s3api get-bucket-location --bucket BUCKET".

Same thing when you try to access a bucket in eu-central-1.

awscli/customizations/s3errormsg.py

@@ -0,0 +1,56 @@
+# Copyright 2014 Amazon.com, Inc. or its affiliates. All Rights Reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License"). You
+# may not use this file except in compliance with the License. A copy of
+# the License is located at
+#
+#     http://aws.amazon.com/apache2.0/
+#
+# or in the "license" file accompanying this file. This file 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.
+"""Give better S3 error messages.
+"""
+from awscli.customizations import utils
+
+
+REGION_ERROR_MSG = (
+    'You can fix this issue by explicity providing the correct region '
+    'location using the --region argument, the AWS_DEFAULT_REGION '
+    'environment variable, or the region variable in the AWS CLI '
+    "configuration file.  You can get the bucket's location by "
+    'running "aws s3api get-bucket-location --bucket BUCKET".'
+)
+
+
+def register_s3_error_msg(event_handlers):
+    event_handlers.register('after-call.s3', enhance_error_msg)
+
+
+def enhance_error_msg(parsed, **kwargs):
+    if parsed is None or 'Error' not in parsed:
+        # There's no error message to enhance so we can continue.
+        return
+    if _is_sigv4_error_message(parsed):
+        message = (
+            'You are attempting to operate on a bucket in a region '
+            'that requires Signature Version 4.  '
+        )
+        message += REGION_ERROR_MSG
+        parsed['Error']['Message'] = message
+    elif _is_permanent_redirect_message(parsed):
+        endpoint = parsed['Error']['Endpoint']
+        message = parsed['Error']['Message']
+        new_message = message[:-1] + ': %s\n' % endpoint
+        new_message += REGION_ERROR_MSG
+        parsed['Error']['Message'] = new_message
+
+
+def _is_sigv4_error_message(parsed):
+    return ('Please use AWS4-HMAC-SHA256' in
+            parsed.get('Error', {}).get('Message', ''))
+
+
+def _is_permanent_redirect_message(parsed):
+    return parsed.get('Error', {}).get('Code', '') == 'PermanentRedirect'

awscli/handlers.py

@@ -47,14 +47,18 @@
 from awscli.customizations.emr.emr import emr_initialize
 from awscli.customizations.cloudsearchdomain import register_cloudsearchdomain
 from awscli.customizations.s3endpoint import register_s3_endpoint
+from awscli.customizations.s3errormsg import register_s3_error_msg
 
 
 def awscli_initialize(event_handlers):
     event_handlers.register('load-cli-arg', uri_param)
     param_shorthand = ParamShorthand()
     event_handlers.register('process-cli-arg', param_shorthand)
+    # The s3 error mesage needs to registered before the
+    # generic error handler.
+    register_s3_error_msg(event_handlers)
     error_handler = ErrorHandler()
-    event_handlers.register('after-call.*.*', error_handler)
+    event_handlers.register('after-call', error_handler)
 #    # The following will get fired for every option we are
 #    # documenting.  It will attempt to add an example_fn on to
 #    # the parameter object if the parameter supports shorthand

tests/unit/customizations/test_s3errormsg.py

@@ -0,0 +1,69 @@
+# Copyright 2014 Amazon.com, Inc. or its affiliates. All Rights Reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License"). You
+# may not use this file except in compliance with the License. A copy of
+# the License is located at
+#
+#     http://aws.amazon.com/apache2.0e
+#
+# or in the "license" file accompanying this file. This file 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.
+import copy
+
+from awscli.testutils import unittest
+from awscli.customizations import s3errormsg
+
+
+class TestGetRegionFromEndpoint(unittest.TestCase):
+
+    def test_sigv4_error_message(self):
+        parsed = {
+            'Error': {
+                'Message': 'Please use AWS4-HMAC-SHA256'
+            }
+        }
+        s3errormsg.enhance_error_msg(parsed)
+        # We should say how to fix the issue.
+        self.assertIn('You can fix this issue',
+                      parsed['Error']['Message'])
+        # We should mention the --region argument.
+        self.assertIn('--region', parsed['Error']['Message'])
+        # We should mention get-bucket-location
+        self.assertIn('get-bucket-location', parsed['Error']['Message'])
+
+    def test_301_error_message(self):
+        parsed = {
+            'Error': {
+                'Code': 'PermanentRedirect',
+                'Message': "Please use the correct endpoint.",
+                'Endpoint': "myendpoint",
+            }
+        }
+        s3errormsg.enhance_error_msg(parsed)
+        # We should include the endpoint in the error message.
+        error_message = parsed['Error']['Message']
+        self.assertIn('myendpoint', error_message)
+
+    def test_error_message_not_enhanced(self):
+        parsed = {
+            'Error': {
+                'Message': 'This is a different error message.',
+                'Code': 'Other Message'
+            }
+        }
+        expected = copy.deepcopy(parsed)
+        s3errormsg.enhance_error_msg(parsed)
+        # Nothing should have changed
+        self.assertEqual(parsed, expected)
+
+    def test_not_an_error_message(self):
+        parsed = {
+            'Success': 'response',
+            'ResponseMetadata': {}
+        }
+        expected = copy.deepcopy(parsed)
+        s3errormsg.enhance_error_msg(parsed)
+        # Nothing should have changed
+        self.assertEqual(parsed, expected)