cmd/bent: fixed error handling in docopy closure.

Change-Id: Icb6f96ede3bda73a026f8037e3be80f608e9df4b
Reviewed-on: https://go-review.googlesource.com/c/benchmarks/+/674375
Reviewed-by: David Chase <drchase@google.com>
Auto-Submit: David Chase <drchase@google.com>
Reviewed-by: Michael Pratt <mpratt@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>

cmd/bent/bent.go

diff --git a/cmd/bent/bent.go b/cmd/bent/bent.go
index 77dbf8f..aba1d22 100644
--- a/cmd/bent/bent.go
+++ b/cmd/bent/bent.go
@@ -675,7 +675,7 @@
 			todo.Configurations[ci] = config
 
 			docopy := func(from, to string) {
-				fileutil.CopyDir(to, from, nil)
+				err := fileutil.CopyDir(to, from, nil)
 				if verbose > 0 || err != nil {
 					fmt.Printf("Copying directory %s to %s, error=%v\n", from, to, err)
 				}