From 009b02bcd521626996d38d4983d02a4cf3d890de Mon Sep 17 00:00:00 2001
From: Jon Michaelchuck <jmichaelchuck@tableau.com>
Date: Mon, 26 Nov 2018 15:56:46 -0800
Subject: [PATCH 1/2] Raise a client error if PutBucketTags request contains
 duplicate keys

A PutBucketTags request with duplicate keys will raise a ClientError
with code InvalidTag and message 'Cannot provide multiple Tags with the
same key'.
---
 moto/s3/exceptions.py    |  9 +++++++++
 moto/s3/models.py        |  5 ++++-
 tests/test_s3/test_s3.py | 18 ++++++++++++++++++
 3 files changed, 31 insertions(+), 1 deletion(-)

diff --git a/moto/s3/exceptions.py b/moto/s3/exceptions.py
index 26515dfd2..f78e24943 100644
--- a/moto/s3/exceptions.py
+++ b/moto/s3/exceptions.py
@@ -178,3 +178,12 @@ class InvalidStorageClass(S3ClientError):
             "InvalidStorageClass",
             "The storage class you specified is not valid",
             *args, **kwargs)
+
+class DuplicateTagKeys(S3ClientError):
+    code = 400
+
+    def __init__(self, *args, **kwargs):
+        super(DuplicateTagKeys, self).__init__(
+            "InvalidTag",
+            "Cannot provide multiple Tags with the same key",
+            *args, **kwargs)
diff --git a/moto/s3/models.py b/moto/s3/models.py
index bb4d7848c..fd53417fa 100644
--- a/moto/s3/models.py
+++ b/moto/s3/models.py
@@ -15,7 +15,7 @@ from bisect import insort
 from moto.core import BaseBackend, BaseModel
 from moto.core.utils import iso_8601_datetime_with_milliseconds, rfc_1123_datetime
 from .exceptions import BucketAlreadyExists, MissingBucket, InvalidPart, EntityTooSmall, MissingKey, \
-    InvalidNotificationDestination, MalformedXML, InvalidStorageClass
+    InvalidNotificationDestination, MalformedXML, InvalidStorageClass, DuplicateTagKeys
 from .utils import clean_key_name, _VersionedKeyStore
 
 UPLOAD_ID_BYTES = 43
@@ -773,6 +773,9 @@ class S3Backend(BaseBackend):
         return key
 
     def put_bucket_tagging(self, bucket_name, tagging):
+        tag_keys = [tag.key for tag in tagging.tag_set.tags]
+        if len(tag_keys) != len(set(tag_keys)):
+            raise DuplicateTagKeys()
         bucket = self.get_bucket(bucket_name)
         bucket.set_tags(tagging)
 
diff --git a/tests/test_s3/test_s3.py b/tests/test_s3/test_s3.py
index 6e339abb6..ffafc0dfd 100644
--- a/tests/test_s3/test_s3.py
+++ b/tests/test_s3/test_s3.py
@@ -1553,6 +1553,24 @@ def test_boto3_put_bucket_tagging():
     })
     resp['ResponseMetadata']['HTTPStatusCode'].should.equal(200)
 
+    # With duplicate tag keys:
+    with assert_raises(ClientError) as err:
+        resp = s3.put_bucket_tagging(Bucket=bucket_name,
+                                     Tagging={
+                                         "TagSet": [
+                                             {
+                                                 "Key": "TagOne",
+                                                 "Value": "ValueOne"
+                                             },
+                                             {
+                                                 "Key": "TagOne",
+                                                 "Value": "ValueOneAgain"
+                                             }
+                                         ]
+                                     })
+    e = err.exception
+    e.response["Error"]["Code"].should.equal("InvalidTag")
+    e.response["Error"]["Message"].should.equal("Cannot provide multiple Tags with the same key")
 
 @mock_s3
 def test_boto3_get_bucket_tagging():

From d29869bf9b678c5573f0ff343dd204c2459142a3 Mon Sep 17 00:00:00 2001
From: Jon Michaelchuck <jmichaelchuck@tableau.com>
Date: Tue, 27 Nov 2018 08:32:30 -0800
Subject: [PATCH 2/2] flake8 fix

---
 moto/s3/exceptions.py | 1 +
 1 file changed, 1 insertion(+)

diff --git a/moto/s3/exceptions.py b/moto/s3/exceptions.py
index f78e24943..c7d82ddfd 100644
--- a/moto/s3/exceptions.py
+++ b/moto/s3/exceptions.py
@@ -179,6 +179,7 @@ class InvalidStorageClass(S3ClientError):
             "The storage class you specified is not valid",
             *args, **kwargs)
 
+
 class DuplicateTagKeys(S3ClientError):
     code = 400