message: Throw nicer error for dropout
  Summary: Ref T22813
  Reviewers: #tensorflow, davidn, #framework_ip_review_-_any_oss_or_third-party_code_use_has_been_approved, hakons
  Subscribers: hakons
  Maniphest Tasks: T22813
diff: @@ -27,6 +27,7 @@ def dropout(x,
  rate=0.5,
  seed_modifier=1,
  noise_shape=None,
  + scale=None,
  name=None):
  """This targets the PopLibs Poprand operation, optimized for execution
  on the IPU.
  @@ -44,6 +45,7 @@ def dropout(x,
  the seed.
  noise_shape: An optional parameter that determines the shape of the dropout.
  Regular, unshaped dropout used if not specified.
  + scale: No longer valid.
  name: Optional op name.
  Returns:
  @@ -51,6 +53,11 @@ def dropout(x,
  other parameters.
  """
  + if scale:
  + raise RuntimeError(
  + "Setting the `scale` parameter in dropout is not supported. Elements "
  + "are scaled up by `1.0 / (1 - rate)` automatically.")
  +
  # Rate is a probability between 0 and 1. Specifically the rate that a variable
  # will be dropped out.
  if rate >= 1.0 or rate < 0.0:
  