test_plots SIGKILL in autopkgtest/CI

[NGC2023]

Hi,
In Debian, test_plots leave figures open, which can accumulate and increase memory usage in constrained environments (autopkgtest/CI), leading to SIGKILL. I have created a patch to address this issue.

--- a/skopt/tests/test_plots.py
+++ b/skopt/tests/test_plots.py
@@ -23,6 +23,16 @@ from skopt.plots import (
 )
 from skopt.space import Categorical, Integer
 
+@pytest.fixture(autouse=True)
+def _close_plots():
+    """
+    Ensure matplotlib figures created during plotting tests are released.
+
+    Without this, figures can accumulate across tests and cause excessive
+    memory usage in constrained environments (e.g. CI/autopkgtest).
+    """
+    yield
+    plt.close("all")
 
 def save_axes(ax, filename):
     """Save matplotlib axes `ax` to an image `filename`."""