Fix the return information for GetDepChangesForChange.

That function returns a tuple of lists of objects, not a tuple of the objects
themselves.

BUG=None
TEST=Ran run_tests.

Change-Id: Ic32058501aba2566a76dca80e4173d333d02556a
Reviewed-on: https://chromium-review.googlesource.com/200643
Reviewed-by: Yu-Ju Hong <yjhong@chromium.org>
Commit-Queue: Gabe Black <gabeblack@chromium.org>
Tested-by: Gabe Black <gabeblack@chromium.org>
diff --git a/buildbot/validation_pool.py b/buildbot/validation_pool.py
index b0fdbac..abc44ea 100644
--- a/buildbot/validation_pool.py
+++ b/buildbot/validation_pool.py
@@ -734,8 +734,8 @@
     """Look up the Gerrit/CQ dependency changes for |change|.
 
     Returns:
-      A tuple of GerritPatch objects which are change's Gerrit
-      dependencies, and CQ dependencies.
+      (gerrit_deps, cq_deps): The change's Gerrit dependencies and CQ
+      dependencies, as lists of GerritPatch objects.
 
     Raises:
       DependencyError: If we could not resolve a dependency.