make version of ts_mon compatible with appengine

infra_libs/ts_mon/common/test/distribution_test.py

 # Copyright 2015 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import unittest
 
-from infra_libs.ts_mon import distribution
+try:
+  from infra_libs.ts_mon.common import distribution
+except ImportError: # pragma: no cover
+  from common import distribution
 
 
 class BucketerTestBase(unittest.TestCase):
   def assertBucketCounts(self, b, expected_total):
     self.assertEquals(expected_total - 2, b.num_finite_buckets)
     self.assertEquals(expected_total, b.total_buckets)
     self.assertEquals(0, b.underflow_bucket)
     self.assertEquals(expected_total - 1, b.overflow_bucket)
 
   def assertBoundaries(self, b, expected_finite_upper_boundaries):
@@ skipping 137 matching lines @@
 
     self.assertEqual(100, d.sum)
     self.assertEqual(1, d.count)
     self.assertEqual({11: 1}, d.buckets)
 
     d.add(1000000)
 
     self.assertEqual(1000100, d.sum)
     self.assertEqual(2, d.count)
     self.assertEqual({11: 2}, d.buckets)