Over in #8056, there was a test failure that appears to be a numpy bug. The test that is failing is TestRandomDist.test_weibull_0, which is:

def test_weibull_0(self):
    assert_equal(np.random.weibull(a=0), 0)
    assert_raises(ValueError, np.random.weibull, a=-0.)

The assertion assert_equal(np.random.weibull(a=0), 0) is failing, because sometimes np.random.weibull(a=0) returns inf:

In [36]: np.__version__
Out[36]: '1.15.4'

In [37]: np.random.seed(123)

In [38]: np.random.weibull(a=0, size=10)
Out[38]: array([inf,  0.,  0.,  0., inf,  0., inf, inf,  0.,  0.])

Those inf values should not be there. I get the same result with the current master branch, '1.16.0.dev0+e34f5bb'.