test_wren: load numpy itself, so the BLAS test passes alone

backend/tests/flow/test_wren.py

@@ -401,9 +401,12 @@ def test_a_trained_model_is_read_from_the_artifact_store(fake_wren, tmp_path):
 
 
 def test_the_model_runs_on_one_blas_thread(fake_wren, monkeypatch):
-    """About twice as fast for a model this small; numpy is loaded by `mlp`."""
+    """About twice as fast for a model this small."""
     from threadpoolctl import threadpool_info
 
+    # BLAS is only listed once something has loaded it, as wren's numpy does.
+    pytest.importorskip("numpy")
+
     threads: list[int] = []
     act = fake_wren.act