Deprecate the fnmatch module.

Oslo.utils's fnmatch module was added to fix the py2.7 fnmatch module
who was not thread safe [1]. Python 2.7 is no longer supported so now we
can use the stdlib's fnmatch module and deprecate the one of oslo.utils.

[1] https://bugs.python.org/issue23191$
[2] e46a46ba90

Change-Id: I538379f91d2ba415c566ada8d221b62b47ba80bb

oslo_utils/fnmatch.py

@@ -24,6 +24,15 @@ import os
 import posixpath
 import re
 import sys
+import warnings
+
+import debtcollector
+
+warnings.simplefilter("always")
+debtcollector.deprecate(
+    "Using the oslo.utils's 'fnmatch' module is deprecate, "
+    "please use the stdlib `fnmatch` module."
+)
 
 
 if sys.version_info > (2, 7, 9):

releasenotes/notes/deprecate-fnmatch-057a092d434a0c53.yaml

@@ -0,0 +1,5 @@
+---
+deprecations:
+  - |
+    Oslo.utils's ``fnmatch`` module is deprecated, please use the stdlib
+    ``fnmatch`` module which is thread safe for python 3+.