[prebuilt] Add black formatter

Bug: 53031
Change-Id: I90d94b4cd9c822259ee8b97a35daff8e67a4cc7a
Reviewed-on: https://fuchsia-review.googlesource.com/c/infra/prebuilt/+/399547
Commit-Queue: Gary Miguel <garymm@google.com>
Reviewed-by: Ina Huh <ihuh@google.com>
diff --git a/cipd.ensure b/cipd.ensure
index b3c20ca..0da1b0e 100644
--- a/cipd.ensure
+++ b/cipd.ensure
@@ -11,6 +11,10 @@
 
 @Subdir tools
 
+# Black formatter
+# To update, see https://fuchsia.googlesource.com/infra/black/+/master/
+fuchsia/tools/black/${platform} version:19.10b0
+
 # Buildbucket CLI
 # TODO(53793): Do not bump until the regression is resolved.
 infra/tools/bb/${platform} git_revision:fa6d9b62c88a7f4184f2e041819d781ca3847908