class RSpec::Mocks::ErrorGenerator

def expectation_on_nil_message(method_name)
  "An expectation of `:#{method_name}` was set on `nil`. " \
  "To allow expectations on `nil` and suppress this message, set `RSpec::Mocks.configuration.allow_message_expectations_on_nil` to `true`. " \
  "To disallow expectations on `nil`, set `RSpec::Mocks.configuration.allow_message_expectations_on_nil` to `false`"
end