message: Add region tags to Python streaming aead example.
diff: # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  # See the License for the specific language governing permissions and
  # limitations under the License.
  +
  +# [START streaming-aead-example]
  """A command-line utility for using streaming AEAD for a file.
  It loads cleartext keys from disk - this is not recommended!
  @@ -159,3 +161,5 @@ if __name__ == '__main__':
  flags.mark_flag_as_required('input_path')
  flags.mark_flag_as_required('output_path')
  app.run(main)
  +
  +# [END streaming-aead-example]
  