Removed the shape validation check to even work for last dimensional shape as 1.

Modified the `test_dirichlet` function to check for the same.

Author: Sayam753

pymc3/distributions/multivariate.py

@@ -522,7 +522,6 @@ def logp(self, value):
             tt.sum(logpow(value, a - 1) - gammaln(a), axis=-1) + gammaln(tt.sum(a, axis=-1)),
             tt.all(value >= 0),
             tt.all(value <= 1),
-            np.logical_not(a.broadcastable[-1]),
             tt.all(a > 0),
             broadcast_conditions=False,
         )

pymc3/tests/test_distributions.py

@@ -1692,7 +1692,7 @@ def test_lkj(self, x, eta, n, lp):
         decimals = select_by_precision(float64=6, float32=4)
         assert_almost_equal(model.fastlogp(pt), lp, decimal=decimals, err_msg=str(pt))
 
-    @pytest.mark.parametrize("n", [2, 3])
+    @pytest.mark.parametrize("n", [1, 2, 3])
     def test_dirichlet(self, n):
         self.pymc3_matches_scipy(Dirichlet, Simplex(n), {"a": Vector(Rplus, n)}, dirichlet_logpdf)