Make StudentT/AsymmetricLaplace .dist() signatures consistent

GOVERNANCE.md

@@ -833,3 +833,4 @@ extra benefits but those will be related to the conference, not the Project.
 * Sharan Yalburgi (GSoC 2018)
 * Taku Yoshioka
 * Tirth Patel (GSoC 2020)
+

pymc/distributions/continuous.py

@@ -1662,7 +1662,7 @@ class AsymmetricLaplace(Continuous):
     rv_op = asymmetriclaplace
 
     @classmethod
-    def dist(cls, b, kappa, mu=0, *args, **kwargs):
+    def dist(cls, kappa, mu, b, *args, **kwargs):
         b = at.as_tensor_variable(floatX(b))
         kappa = at.as_tensor_variable(floatX(kappa))
         mu = mu = at.as_tensor_variable(floatX(mu))
@@ -1901,7 +1901,7 @@ class StudentT(Continuous):
     rv_op = studentt
 
     @classmethod
-    def dist(cls, nu, mu=0, lam=None, sigma=None, *args, **kwargs):
+    def dist(cls, nu=1, mu=0, sigma=None, lam=None, *args, **kwargs):
         nu = at.as_tensor_variable(floatX(nu))
         lam, sigma = get_tau_sigma(tau=lam, sigma=sigma)
         sigma = at.as_tensor_variable(sigma)