message: Fix wrong small-size assumption
  Summary: Some files can be large. Better to break them up for hashing.
diff: @@ -61,6 +61,8 @@ class CompressionEntry(typing.NamedTuple):
  class _Compressor(ABC):
  + _BUF_SIZE: int = 128 * 1024
  +
  def __init__(self, checksum_name: typing.Optional[str]) -> None:
  self.checksum_name = checksum_name
  self.do_checksum: bool = checksum_name is not None
  @@ -75,10 +77,14 @@ class _Compressor(ABC):
  hash = hashlib.md5()
  self.hash = hash
  - # Files should be small enough to read into memory.
  - assert os.path.getsize(file_path) < 10000000
  + # Gotta read this block-wise, as some files may be
  + # quite large.
  with open(file_path, "rb") as f:
  - hash.update(f.read())
  + while True:
  + data = f.read(_Compressor._BUF_SIZE)
  + if not data:
  + break
  + hash.update(data)
  @abstractmethod
  def _handle_file_impl(self, file_path: str, file_name: str) -> None:
  