Roll recipe dependencies (trivial).

This is an automated CL created by the recipe roller. This CL rolls recipe
changes from upstream projects (e.g. depot_tools) into downstream projects
(e.g. tools/build).


More info is at https://goo.gl/zkKdpD. Use https://goo.gl/noib3a to file a bug.
recipe_engine:
  https://crrev.com/c916898b8189866a0bf43fe15c800e4fe6d4a19e [context] fix treatment of None in env. (iannucci@chromium.org)


TBR=iannucci@chromium.org

Recipe-Tryjob-Bypass-Reason: Autoroller
Bugdroid-Send-Email: False
Change-Id: I96a7fb05593c4e946faa581a67bcc5f2ecdcace4
Reviewed-on: https://chromium-review.googlesource.com/527913Reviewed-by: Recipe Roller <recipe-roller@chromium.org>
Commit-Queue: Recipe Roller <recipe-roller@chromium.org>

infra/config/recipes.cfg

@@ -15,7 +15,7 @@
   "deps": {
     "recipe_engine": {
       "branch": "master",
-      "revision": "c40412cbc4e1b8ee1e6eba2e88328ca71c6ec1e4",
+      "revision": "c916898b8189866a0bf43fe15c800e4fe6d4a19e",
       "url": "https://chromium.googlesource.com/external/github.com/luci/recipes-py.git"
     }
   },