Bump pyyaml version

LindsayHill · web-flow · commit 8c70607ca0cc · 2019-02-05T13:19:47.000-08:00
diff --git a/.circle/requirements.txt b/.circle/requirements.txt
@@ -1,3 +1,3 @@
 jsonschema==2.5.1
-pyyaml==3.11
+pyyaml==4.2b1
 requests[security]==2.21.0
