class RSpec::Mocks::ErrorGenerator

def self.raise_double_negation_error(wrapped_expression)
  raise "Isn't life confusing enough? You've already set a " +
        "negative message expectation and now you are trying to " +
        "negate it again with `never`. What does an expression like " +
        "`#{wrapped_expression}.not_to receive(:msg).never` even mean?"
end