Merge changes If7c8d38f,I7117dd19,Iaa5006e3,I3a568361,I37df06e4, ...

* changes:
  adb: report connection status when we're unauthorized.
  adb: disable test_device.FileOperationsTest.test_pull_symlink_dir.
  adb: fix test_device.FileOperationsTest.test_push_empty
  adb: switch test_adb.py over to double quotes.
  adb: make test_adb.py work on windows.
  adb: switch test_adb.py to python3.