fix warning used by cbook.warn_deprecated()

sameshl · sameshl · commit 4ac14da8a766 · 2019-09-22T00:29:48.000+05:30
change warning class from UserWarning to MatplotlibDeprecationWarning closes #15289
diff --git a/lib/matplotlib/cbook/deprecation.py b/lib/matplotlib/cbook/deprecation.py
@@ -108,7 +108,7 @@ def warn_deprecated(
         since, message, name, alternative, pending, obj_type, addendum,
         removal=removal)
     from . import _warn_external
-    _warn_external(warning)
+    _warn_external(warning, category=MatplotlibDeprecationWarning)
 
 
 def deprecated(since, *, message='', name='', alternative='', pending=False,
