Move gerrit_helper and patch into reusable locations.

Specifically,
chromite.buildbot.gerrit_helper*.py -> chromite.lib.gerrit*.py
chromite.buildbot.patch*.py -> chromite.lib.patch*.py

BUG=chromium-os:32910
TEST=run_tests

Change-Id: I4f3fe3fc26d30a350c4fa73ae78715c422909cb7
Reviewed-on: https://gerrit.chromium.org/gerrit/35179
Commit-Ready: Brian Harring <ferringb@chromium.org>
Reviewed-by: Brian Harring <ferringb@chromium.org>
Tested-by: Brian Harring <ferringb@chromium.org>
diff --git a/scripts/cbuildbot.py b/scripts/cbuildbot.py
index 1a7b7e9..6748b35 100644
--- a/scripts/cbuildbot.py
+++ b/scripts/cbuildbot.py
@@ -26,8 +26,6 @@
 from chromite.buildbot import cbuildbot_stages as stages
 from chromite.buildbot import cbuildbot_results as results_lib
 from chromite.buildbot import constants
-from chromite.buildbot import gerrit_helper
-from chromite.buildbot import patch as cros_patch
 from chromite.buildbot import remote_try
 from chromite.buildbot import repository
 from chromite.buildbot import tee
@@ -37,7 +35,9 @@
 from chromite.lib import cleanup
 from chromite.lib import commandline
 from chromite.lib import cros_build_lib
+from chromite.lib import gerrit
 from chromite.lib import osutils
+from chromite.lib import patch as cros_patch
 from chromite.lib import sudo
 
 
@@ -111,14 +111,14 @@
     trybot_patch_pool.TrybotPatchPool object.
 
   Raises:
-    gerrit_helper.GerritException, cros_patch.PatchException
+    gerrit.GerritException, cros_patch.PatchException
   """
   gerrit_patches = []
   local_patches = []
   remote_patches = []
 
   if options.gerrit_patches:
-    gerrit_patches = gerrit_helper.GetGerritPatchInfo(
+    gerrit_patches = gerrit.GetGerritPatchInfo(
         options.gerrit_patches)
     for patch in gerrit_patches:
       if patch.IsAlreadyMerged():