histogram_verifier: clarify failure message

The word "bucket" is vague, since we often use it to refer to google
storage (GS) buckets. That makes this failure message smell a little
like an infrastructure issue at first glance, even though it isn't.
Clarify it.

BUG=None
TEST=None

Change-Id: Ib3c5b8094798cb4df85f75f90329a1e988d08796
Reviewed-on: https://chromium-review.googlesource.com/334041
Commit-Ready: Aviv Keshet <akeshet@chromium.org>
Tested-by: Aviv Keshet <akeshet@chromium.org>
Reviewed-by: Todd Broch <tbroch@chromium.org>
diff --git a/client/cros/video/histogram_verifier.py b/client/cros/video/histogram_verifier.py
index 235c84a..bf0c948 100644
--- a/client/cros/video/histogram_verifier.py
+++ b/client/cros/video/histogram_verifier.py
@@ -22,8 +22,8 @@
 
      """
      bucket_pattern = '\n'+ str(histogram_bucket_value) +'.*100\.0%.*'
-     error_msg_format = ('{} not loaded or bucket not found '
-                         'or bucket found at < 100%')
+     error_msg_format = ('{} not loaded or histogram bucket not found '
+                         'or histogram bucket found at < 100%')
      tab = cr.browser.tabs.New()
 
      def loaded():