class I18n::Config

def missing_interpolation_argument_handler

is missing. MissingInterpolationArgument will be raised by default.
Returns the current handler for situations when interpolation argument

def missing_interpolation_argument_handler
  @@missing_interpolation_argument_handler ||= lambda do |missing_key, provided_hash, string|
    raise MissingInterpolationArgument.new(missing_key, provided_hash, string)
  end
end