Don't warn when accessing deprecated properties from the class.

anntzer · anntzer · commit bb5d40071d19 · 2018-10-27T22:15:29.000+02:00
Otherwise, we get a lot of spurious warnings from inspection tools such
as pydoc.
diff --git a/lib/matplotlib/cbook/deprecation.py b/lib/matplotlib/cbook/deprecation.py
@@ -201,18 +201,21 @@ def finalize(wrapper, new_doc):
 
             class _deprecated_property(property):
                 def __get__(self, instance, owner):
-                    from . import _warn_external
-                    _warn_external(message, category)
+                    if instance is not None:
+                        from . import _warn_external
+                        _warn_external(message, category)
                     return super().__get__(instance, owner)
 
                 def __set__(self, instance, value):
-                    from . import _warn_external
-                    _warn_external(message, category)
+                    if instance is not None:
+                        from . import _warn_external
+                        _warn_external(message, category)
                     return super().__set__(instance, value)
 
                 def __delete__(self, instance):
-                    from . import _warn_external
-                    _warn_external(message, category)
+                    if instance is not None:
+                        from . import _warn_external
+                        _warn_external(message, category)
                     return super().__delete__(instance)
 
             def finalize(_, new_doc):
