document the reason for the change

stonebig · web-flow · commit 466330b89c95 · 2018-02-28T22:45:54.000+01:00
diff --git a/lib/matplotlib/axes/_subplots.py b/lib/matplotlib/axes/_subplots.py
@@ -173,6 +173,8 @@ def _make_twin_axes(self, *kl, **kwargs):
         """
         from matplotlib.projections import process_projection_requirements
         if 'sharex' in kwargs and 'sharey' in kwargs:
+            # The following line is added in v2.2 to avoid breaking Seaborn,
+            # which currently uses this internal API.          
             if kwargs["sharex"] is not self and kwargs["sharey"] is not self:
                 raise ValueError("Twinned Axes may share only one axis.")
         kl = (self.get_subplotspec(),) + kl
