message: fix missing prop error message for OcticonButton
diff: @@ -16,11 +16,11 @@ describe('OcticonButton', () => {
  })
  it('renders a button with an Octicon', () => {
  - expect(render(<OcticonButton icon={Circle} />)).toMatchSnapshot()
  + expect(render(<OcticonButton icon={Circle} label="circle" />)).toMatchSnapshot()
  })
  it('respects the "disabled" prop', () => {
  - expect(render(<OcticonButton icon={Circle} disabled />).props.disabled).toBe(true)
  + expect(render(<OcticonButton icon={Circle} disabled label="circle" />).props.disabled).toBe(true)
  })
  it('sets "aria-label" to the "label" prop', () => {
  @@ -29,10 +29,10 @@ describe('OcticonButton', () => {
  it('passes the onClick handler to the <button>', () => {
  function click() {}
  - expect(render(<OcticonButton icon={Circle} onClick={click} />).props.onClick).toEqual(click)
  + expect(render(<OcticonButton icon={Circle} onClick={click} label="circle" />).props.onClick).toEqual(click)
  })
  it('passes the "size" prop to the Octicon', () => {
  - expect(render(<OcticonButton icon={Circle} size={128} />)).toMatchSnapshot()
  + expect(render(<OcticonButton icon={Circle} size={128} label="circle" />)).toMatchSnapshot()
  })
  })
  