(core) Import Hashable from six.moves.collections_abc

Summary: Copy of https://github.com/gristlabs/grist-core/pull/136

Test Plan: this

Reviewers: paulfitz

Reviewed By: paulfitz

Differential Revision: https://phab.getgrist.com/D3278

sandbox/grist/engine.py

@@ -14,7 +14,7 @@ from collections import namedtuple, OrderedDict, defaultdict
 
 import six
 from six.moves import zip
-from six.moves.collections_abc import Hashable
+from six.moves.collections_abc import Hashable  # pylint:disable-all
 from sortedcontainers import SortedSet
 
 import acl

sandbox/grist/test_match_counter.py

@@ -5,7 +5,7 @@ import unittest
 
 import six
 from six.moves import xrange
-from six.moves.collections_abc import Hashable
+from six.moves.collections_abc import Hashable  # pylint:disable-all
 
 import match_counter
 from testutil import repeat_until_passes