'a pth file manager should set dirty
if a distribution is in site but also the cwd'

def test_add_from_cwd_site_sets_dirty(self):

    pth = PthDistributions('does-not_exist', [os.getcwd()])
    self.assertTrue((not pth.dirty))
    pth.add(PRDistribution(os.getcwd()))
    self.assertTrue(pth.dirty)
