Make mlflow test optional

pyproject.toml

@@ -136,6 +136,9 @@ ignore = [
     "D",
     "S101", # Use of assert
 ]
+"tests/test_mlflow.py" = [
+    "E402",  # Module level import not at top of file. Needed for importorskip
+]
 "scripts/*" = ["D"]
 
 [tool.ruff.lint.pycodestyle]

tests/test_mlflow.py

@@ -11,13 +11,16 @@
 #   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 #   See the License for the specific language governing permissions and
 #   limitations under the License.
+import pytest
+
+mlflow = pytest.importorskip("mlflow")
+
 import json
 import logging
 from collections import namedtuple
 from pathlib import Path
 
 import arviz as az
-import mlflow
 import numpy as np
 import pandas as pd
 import pymc as pm