Switch to collections.abc.MutableMapping

collections.MutableMapping has been deprecated since Python 3.3 and
is removed in Python 3.10. The functionality should be identical.

Change-Id: Ic96309fef409ba01dd24a3a70ff132a9f5352f9c

oslo_policy/policy.py

@@ -221,7 +221,7 @@ by setting the ``policy_default_rule`` configuration setting to the
 desired rule name.
 """
 
-import collections
+import collections.abc
 import copy
 import logging
 import os
@@ -953,9 +953,9 @@ class Enforcer(object):
         # a method on RequestContext objects that converts attributes of the
         # context object to policy values. However, ``to_policy_values()``
         # doesn't actually return a dictionary, it's a subclass of
-        # collections.MutableMapping, which behaves like a dictionary but
+        # collections.abc.MutableMapping, which behaves like a dictionary but
         # doesn't pass the type check.
-        elif not isinstance(creds, collections.MutableMapping):
+        elif not isinstance(creds, collections.abc.MutableMapping):
             msg = (
                 'Expected type oslo_context.context.RequestContext, dict, or  '
                 'the output of '

oslo_policy/shell.py

@@ -13,7 +13,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-import collections
+import collections.abc
 import sys
 
 from oslo_serialization import jsonutils
@@ -59,7 +59,7 @@ def flatten(d, parent_key=''):
     items = []
     for k, v in d.items():
         new_key = parent_key + '.' + k if parent_key else k
-        if isinstance(v, collections.MutableMapping):
+        if isinstance(v, collections.abc.MutableMapping):
             items.extend(flatten(v, new_key).items())
         else:
             items.append((new_key, v))