Use aspect=1, not aspect=True.

anntzer · anntzer · commit 31ae50fda488 · 2019-06-01T21:01:35.000+02:00
aspect=True seems like an obfuscated way to spell aspect=1 ("equal
aspect").

(Note that this should not be confused with uses of `aspect=True` in
AxesGrid, which is different and actually takes a bool as argument...)
diff --git a/lib/matplotlib/tests/test_arrow_patches.py b/lib/matplotlib/tests/test_arrow_patches.py
@@ -18,8 +18,7 @@ def test_fancyarrow():
     t = ["fancy", "simple", mpatches.ArrowStyle.Fancy()]
 
     fig, axs = plt.subplots(len(t), len(r), squeeze=False,
-                            subplot_kw=dict(aspect=True),
-                            figsize=(8, 4.5))
+                            figsize=(8, 4.5), subplot_kw=dict(aspect=1))
 
     for i_r, r1 in enumerate(r):
         for i_t, t1 in enumerate(t):
