[pybsddb] Use `collections.abc` in Python

[Jan Staněk]

Hello,
in Python 3.9, the ABCs were removed from the stdlib `collections` 
module, now visible only in `collections.abc` module.

I have taken the liberty of preparing a quick patch for the Python3 
parts of this package (see below). Note that this is a best-effort 
attempt, as I'm not very well versed in the codebase.

Hope this helps!

# HG changeset patch
# User Jan Staněk <jstanek at redhat.com>
# Date 1579263565 -3600
#      Fri Jan 17 13:19:25 2020 +0100
# Node ID ce83dd57a7970a020a6d727dbfd5f46723fbda44
# Parent  090c663dc2a1b9544a837ba34358e4fde445b182
python3: Import MutableMapping from collections.abc

diff -r 090c663dc2a1 -r ce83dd57a797 Lib3/bsddb/__init__.py
--- a/Lib3/bsddb/__init__.py	Sun Jul 01 22:17:17 2018 +0200
+++ b/Lib3/bsddb/__init__.py	Fri Jan 17 13:19:25 2020 +0100
@@ -66,8 +66,10 @@

  from weakref import ref

-import collections
-MutableMapping = collections.MutableMapping
+try:
+    from collections.abc import MutableMapping
+except ImportError:
+    from collections import MutableMapping

  class _iter_mixin(MutableMapping):
      def _make_iter_cursor(self):
diff -r 090c663dc2a1 -r ce83dd57a797 Lib3/bsddb/dbobj.py
--- a/Lib3/bsddb/dbobj.py	Sun Jul 01 22:17:17 2018 +0200
+++ b/Lib3/bsddb/dbobj.py	Fri Jan 17 13:19:25 2020 +0100
@@ -28,8 +28,10 @@
  else :
      from . import db

-import collections
-MutableMapping = collections.MutableMapping
+try:
+    from collections.abc import MutableMapping
+except ImportError:
+    from collections import MutableMapping

  class DBEnv:
      def __init__(self, *args, **kwargs):
diff -r 090c663dc2a1 -r ce83dd57a797 Lib3/bsddb/dbshelve.py
--- a/Lib3/bsddb/dbshelve.py	Sun Jul 01 22:17:17 2018 +0200
+++ b/Lib3/bsddb/dbshelve.py	Fri Jan 17 13:19:25 2020 +0100
@@ -48,8 +48,10 @@
  def _dumps(object, protocol):
      return pickle.dumps(object, protocol=protocol)

-import collections
-MutableMapping = collections.MutableMapping
+try:
+    from collections.abc import MutableMapping
+except ImportError:
+    from collections import MutableMapping

  #------------------------------------------------------------------------


-- 
Jan Staněk
Associate Software Engineer
Red Hat EMEA
jstanek at redhat.com     IM: jstanek