MNT: use BytesIO contextmanager

tacaswell · QuLogic · web-flow · commit 5ece54cd9360 · 2022-12-20T09:50:56.000-05:00
Co-authored-by: Elliott Sales de Andrade &lt;quantum.analyst@gmail.com&gt;
diff --git a/lib/matplotlib/tests/test_axes.py b/lib/matplotlib/tests/test_axes.py
@@ -8455,5 +8455,5 @@ def test_zorder_and_explicit_rasterization():
     fig, ax = plt.subplots()
     ax.set_rasterization_zorder(5)
     ln, = ax.plot(range(5), rasterized=True, zorder=1)
-    b = io.BytesIO()
-    fig.savefig(b, format='pdf')
+    with io.BytesIO() as b:
+        fig.savefig(b, format='pdf')
