update msg and add context

Author: cvanelteren

ultraplot/axes/base.py

@@ -2521,6 +2521,9 @@ def _sharey_setup(self, sharey, **kwargs):
         self._share_long_axis(sharey, "left", **kwargs)  # y axis of left panels
         self._share_long_axis(sharey, "right", **kwargs)
 
+    def _share_alty(self, share, side, **kwargs):
+        pass
+
     def _share_short_axis(self, share, side, **kwargs):
         """
         Share the "short" axes of panels in this subplot with other panels.

ultraplot/figure.py

@@ -826,7 +826,7 @@ def _parse_backend(backend=None, basemap=None):
         # Basemap is currently being developed again so are removing the deprecation warning
         if backend == "basemap":
             warnings._warn_ultraplot(
-                f"{backend=} will be deprecated in next major release (v1.6)"
+                f"{backend=} will be deprecated in next major release (v1.60.0). See https://github.com/Ultraplot/ultraplot/pull/243#pullrequestreview-2885501470"
             )
         return backend