Update boto3 from 1.5.18 to 1.5.20 (#7372)

requirements/prod.txt

@@ -88,9 +88,9 @@ celery==4.1.0 \
 botocore==1.8.33 \
     --hash=sha256:7c1341590a05b8c7146def11e76d71b1b0d2ef6fa1f05a177494113f41bd17e9 \
     --hash=sha256:fa29ea54f26b1193682332d3b4cdde7aa79b4eaccb23f70e88672509c24546f4
-boto3==1.5.18 \
-    --hash=sha256:744b5080ea8cefb9d831e21e959ab1bd46a5c0918fdd806534090546137a355a \
-    --hash=sha256:8178acd18c8bc92e35eaf6dd4e9900ccc2ccc927b5d64d42f87816118de67646
+boto3==1.5.20 \
+    --hash=sha256:24f8f919126b8a55ef3be6729243f71ffe4b927408e4a1be4e64671cdb011409 \
+    --hash=sha256:06614d6111c0bcc7e76ef699e4caec0de87217180486e43ec2c353d6f01a409d
 # chardet is required by requests
 chardet==3.0.4 \
     --hash=sha256:fc323ffcaeaed0e0a02bf4d117757b98aed530d9ed4531e3e15460124c106691 \