packages: Add empty endpoint UprevVersionedPackage

TEST=./run_tests
BUG=chromium:985504

Change-Id: If953a934bb347fce67c091c21355fd5d2020866c
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/chromite/+/1737529
Commit-Queue: Evan Hernandez <evanhernandez@chromium.org>
Tested-by: Evan Hernandez <evanhernandez@chromium.org>
Auto-Submit: Evan Hernandez <evanhernandez@chromium.org>
Reviewed-by: David Burger <dburger@chromium.org>
diff --git a/api/controller/packages.py b/api/controller/packages.py
index 7b74ad7..b314091 100644
--- a/api/controller/packages.py
+++ b/api/controller/packages.py
@@ -48,6 +48,13 @@
   for path in uprevved:
     output_proto.modified_ebuilds.add().path = path
 
+def UprevVersionedPackage(_input_proto, _output_proto):
+  """Uprev a versioned package.
+
+  See go/pupr-generator for details about this endpoint.
+  """
+  pass
+
 @validate.require('atom')
 def GetBestVisible(input_proto, output_proto):
   """Returns the best visible PackageInfo for the indicated atom."""