Update run_v1_only tests with proper reasons.

PiperOrigin-RevId: 322386004
Change-Id: I9b292be8ce51118f6537853c14a22da748fcea9d

tensorflow/python/training/sync_replicas_optimizer_test.py

@@ -89,7 +89,8 @@ class SyncReplicasOptimizerTest(test.TestCase):
   def _run(self, train_op, sess):
     sess.run(train_op)
 
-  @test_util.run_v1_only("b/120545219")
+  @test_util.run_v1_only(
+      "This exercises tensor lookup via names which is not supported in V2.")
   def test2Workers(self):
     num_workers = 2
     replicas_to_aggregate = 2
@@ -180,7 +181,8 @@ class SyncReplicasOptimizerTest(test.TestCase):
                         sessions[1].run(var_1_g_1))
 
   # 3 workers and one of them is backup.
-  @test_util.run_v1_only("b/120545219")
+  @test_util.run_v1_only(
+      "This exercises tensor lookup via names which is not supported in V2.")
   def test3Workers1Backup(self):
     num_workers = 3
     replicas_to_aggregate = 2
@@ -268,7 +270,9 @@ class SyncReplicasOptimizerHookTest(test.TestCase):
     with self.assertRaisesRegex(ValueError, "apply_gradient should be called"):
       hook.begin()
 
-  @test_util.run_v1_only("b/120545219")
+  @test_util.run_v1_only(
+      "train.SyncReplicasOptimizer and train.GradientDescentOptimizer "
+      "are V1 only APIs.")
   def testCanCreatedBeforeMinimizeCalled(self):
     """This behavior is required to be integrated with Estimators."""
     opt = training.SyncReplicasOptimizer(
@@ -281,7 +285,8 @@ class SyncReplicasOptimizerHookTest(test.TestCase):
     opt.minimize(v, global_step=global_step)
     hook.begin()
 
-  @test_util.run_v1_only("b/120545219")
+  @test_util.run_v1_only(
+      "train.SyncReplicasOptimizer and train.AdamOptimizer are V1 only APIs.")
   def testFetchVariableList(self):
     opt = training.SyncReplicasOptimizer(
         opt=adam.AdamOptimizer(0.01),