'Test error output from command'

def test_error_output(self):

    cmd = BuildCommand(['/bin/bash', '-c', 'echo    -n    FOOBAR    1>&2'])
    cmd.run()
    self.assertEqual(cmd.output, 'FOOBAR')
    self.assertIsNone(cmd.error)
    cmd = BuildCommand(['/bin/bash', '-c', 'echo    -n    FOOBAR    1>&2'], combine_output=False)
    cmd.run()
    self.assertEqual(cmd.output, '')
    self.assertEqual(cmd.error, 'FOOBAR')
