Added check that nu must be a scalar in MvStudentTRV

[sagartomar]

This should fix issue #5214

[codecov]

Codecov Report

Merging #5241 (24316b2) into main (a4f9657) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##             main    #5241   +/-   ##
=======================================
  Coverage   79.12%   79.13%           
=======================================
  Files          88       88           
  Lines       14306    14311    +5     
=======================================
+ Hits        11320    11325    +5     
  Misses       2986     2986           

Impacted Files	Coverage Δ
pymc/distributions/multivariate.py	73.39% <100.00%> (+0.19%)	⬆️

[ricardoV94]

Looks great. I left a suggestion below, and we should add a test that covers this branch.

Perhaps in test_distributions_random you can add something along the lines of the following one:

pymc/pymc/tests/test_distributions_random.py

Lines 1622 to 1632 in 95bd5e5

	def test_errors(self):
	msg = "MatrixNormal doesn't support size argument"
	with pm.Model():
	with pytest.raises(NotImplementedError, match=msg):
	matrixnormal = pm.MatrixNormal(
	"matnormal",
	mu=np.random.random((3, 3)),
	rowcov=np.eye(3),
	colcov=np.eye(3),
	size=15,
	)

[michaelosthege]

Looks good!
I like the re.escape(msg) it always takes me ages to find the right escape syntax..

[ricardoV94]

Looks great