fix test (#2549)

address issues building mlflow model in GHA test env

test/unit/cli/fixtures/__init__.py

@@ -0,0 +1,5 @@
+from .mlflow_model_fixture import FakeModel
+
+
+def _load_pyfunc(data_path):
+    return FakeModel()

test/unit/cli/fixtures/mlflow_model_fixture.py

@@ -0,0 +1,11 @@
+import mlflow
+
+
+class FakeModel(mlflow.pyfunc.PythonModel):
+    def __init__(self, input_to_output: dict = {}):
+        self.input_to_output = input_to_output
+
+    def predict(self, model_input) -> None:
+        # this stdout output is useful for validating the input in a test, noting that this model will be invoked in a
+        # subprocess, so stdout is one means of communicating information back to the test code
+        print(f"__MODEL_INPUT__={model_input.iloc[0][0]}")