This apparently works fine on the try bots, but some development desktops have a system level instillation of protobuf at

/usr/lib/python2.7/dist-packages/google/protobuf

This causes all of the integration tests that use the python server to fail. Steps to repro
1. ninja -C out/Default -j 1000 chrome
2. ninja -C out/Default -j 1000 sync_integration_tests
3. out/Default/sync_integration_tests --gtest_filter=MigrationSingleClientTest.PrefsOnlyTriggerNotification

Traceback (most recent call last):
  File "/usr/local/google/home/skym/chromiumSource/linux/src/components/sync/tools/testserver/sync_testserver.py", line 24, in <module>
    import chromiumsync
  File "/usr/local/google/home/skym/chromiumSource/linux/src/components/sync/tools/testserver/chromiumsync.py", line 26, in <module>
    import app_list_specifics_pb2
  File "/usr/local/google/home/skym/chromiumSource/linux/src/out/Default/pyproto/components/sync/protocol/app_list_specifics_pb2.py", line 9, in <module>
    from google.protobuf import symbol_database as _symbol_database
  File "/usr/local/google/home/skym/chromiumSource/linux/src/out/Default/pyproto/google/protobuf/symbol_database.py", line 180, in <module>
    _DEFAULT = SymbolDatabase(pool=descriptor_pool.Default())
AttributeError: 'module' object has no attribute 'Default'
[42020:42020:0923/144155:275935356285:ERROR:local_test_server_posix.cc(163)] Could not read server_data_len
../../chrome/browser/sync/test/integration/sync_test.cc:882: Failure

This was previously encountered here https://groups.google.com/a/chromium.org/forum/#!msg/chromium-dev/GndDLYTrPaE/RmlA4DocBgAJ , where it was suggested that we use virtualenv to solve this conflict.

It looks like there's already an existing example in chromium that uses virtualenv https://cs.chromium.org/chromium/src/tools/android/loading/cloud/backend/startup-script.sh