Update boto3 from 1.9.20 to 1.9.21

requirements/prod_common.txt

@@ -103,9 +103,9 @@ billiard==3.5.0.4 \
 bleach==3.0.1 \
     --hash=sha256:f680cc08e2eea821f3173b875f68763960006f1e764c92b5d2b8354af3a47468 \
     --hash=sha256:c39d25d9ada62009853b0281efdc35a792db8cdee89465433e6d0aaaf5defc3f
-boto3==1.9.20 \
-    --hash=sha256:3e31a82b3739e44dc47ab99f514ff9ef9b230f38ecf4dbe04a90edc53b284468 \
-    --hash=sha256:0409ee2b927a8767ca629c5d2f09799e937636ec0f0123842b63f526ec170c0c
+boto3==1.9.21 \
+    --hash=sha256:606c82cb388dbf92a988d01e77157f566356e69d0e696232ccce19677cca0723 \
+    --hash=sha256:f6b9dd8ab398bd563ca43de7f758dd5facbca82e0db8a0dca99d636b36878d6e
 celery==4.1.1 \
     --hash=sha256:6fc4678d1692af97e137b2a9f1c04efd8e7e2fb7134c5c5ad60738cdd927762f \
     --hash=sha256:d1f2a3359bdbdfb344edce98b8e891f5fe64f8a11c5a45538ec20ac237c971f5 # pyup: <4.2