Skip variational inference tests.

Because of a pytest issue these trigger issue pymc-devs#3775.

Author: rpgoldman

pymc3/tests/conftest.py

@@ -35,3 +35,6 @@ def seeded_test():
     # TODO: use this instead of SeededTest
     np.random.seed(42)
     pm.set_tt_rng(42)
+
+
+collect_ignore = ["test_variational_inference.py"]

pymc3/tests/test_variational_inference.py

@@ -685,7 +685,6 @@ def fit_kwargs(inference, use_minibatch):
         key = 'full'
     return _select[(type(inference), key)]
 
-
 @pytest.mark.run('first')
 def test_fit_oo(inference,
                 fit_kwargs,