Merge pull request matplotlib#23289 from anntzer/16

MNT: Properly make Name.hexify go through a deprecation cycle.

Author: tacaswell

doc/api/next_api_changes/deprecations/23289-AL.rst

@@ -0,0 +1,3 @@
+``backend_pdf.Name.hexify``
+~~~~~~~~~~~~~~~~~~~~~~~~~~~
+... is deprecated with no replacement.

lib/matplotlib/backends/backend_pdf.py

@@ -392,6 +392,11 @@ def __lt__(self, other):
     def __hash__(self):
         return hash(self.name)
 
+    @staticmethod
+    @_api.deprecated("3.6")
+    def hexify(match):
+        return '#%02x' % ord(match.group())
+
     def pdfRepr(self):
         return b'/' + self.name