message: Increase protobuf PIP requirement to >=3.8.0
  This is required in order to get , which adds a `RepeatedCompositeContainer.append()` method.
  Thanks to for raising this issue. Fixes
diff: @@ -61,7 +61,7 @@ REQUIRED_PACKAGES = [
  'numpy >= 1.16.0, < 2.0',
  'opt_einsum >= 2.3.2',
  'six >= 1.10.0',
  - 'protobuf >= 3.6.1',
  + 'protobuf >= 3.8.0',
  'tensorboard >= 2.0.0, < 2.1.0',
  'tensorflow_estimator >= 2.0.0, < 2.1.0',
  'termcolor >= 1.1.0',
  