sdk_stages_unittest: skip flaky test

BUG=chromium:554563
TEST=None

Change-Id: Ic127b2c4aeb76a9e6edaf2a15ca334cc7e06ff76
Reviewed-on: https://chromium-review.googlesource.com/312127
Commit-Ready: Aviv Keshet <akeshet@chromium.org>
Tested-by: Aviv Keshet <akeshet@chromium.org>
Reviewed-by: David James <davidjames@chromium.org>
diff --git a/cbuildbot/stages/sdk_stages_unittest.py b/cbuildbot/stages/sdk_stages_unittest.py
index 96e3d11..c933b86 100644
--- a/cbuildbot/stages/sdk_stages_unittest.py
+++ b/cbuildbot/stages/sdk_stages_unittest.py
@@ -8,6 +8,7 @@
 
 import json
 import os
+import unittest
 
 from chromite.cbuildbot import commands
 from chromite.cbuildbot import constants
@@ -221,6 +222,8 @@
   def ConstructStage(self):
     return sdk_stages.SDKPackageToolchainOverlaysStage(self._run)
 
+  # TODO(akeshet): determine why this test is flaky
+  @unittest.skip("Skip flaky test.")
   def testTarballCreation(self):
     """Tests that tarballs are created for all board toolchains."""
     self._Prepare('chromiumos-sdk')