Import ABC from collections.abc instead of collections for Python 3.9 compatibility.

misc/table_html_app.py

@@ -88,6 +88,9 @@ class BasicRender(object):
         self.autotable_render = AutoTableRenderer()
 
     def render_response(self, request, context, _route):
+        try:
+            from collections.abc import Sized
+        except ImportError:
             from collections import Sized
         if isinstance(context, basestring):  # already serialized
             if self._guess_json(context):

tests/test_dictutils.py

@@ -88,10 +88,14 @@ def test_clear():
 
 
 def test_types():
-    import collections
+    try:
+        from collections.abc import MutableMapping
+    except ImportError:
+        from collections import MutableMapping
+
     omd = OMD()
     assert isinstance(omd, dict)
-    assert isinstance(omd, collections.MutableMapping)
+    assert isinstance(omd, MutableMapping)
 
 
 def test_multi_correctness():