message: Pin gast.
  Sadly, gast needs to be pinned to 0.3.3 as otherwise ecosystem packages break.
diff: @@ -78,7 +78,6 @@ REQUIRED_PACKAGES = [
  'absl-py ~= 0.10',
  'astunparse ~= 1.6.3',
  'flatbuffers ~= 1.12.0',
  - 'gast ~= 0.4',
  'google_pasta ~= 0.2',
  'h5py ~= 2.10.0',
  'keras_preprocessing ~= 1.1.2',
  @@ -90,6 +89,9 @@ REQUIRED_PACKAGES = [
  'typing_extensions ~= 3.7.4',
  'wheel ~= 0.35',
  'wrapt ~= 1.12.1',
  + # These packages needs to be pinned exactly as newer versions are
  + # incompatible with the rest of the ecosystem
  + 'gast == 0.3.3',
  # TensorFlow ecosystem packages that TF exposes API for
  # These need to be in sync with the existing TF version
  # They are updated during the release process
  