Import ABC from collections.abc

pgpy/packet/fields.py

@@ -11,6 +11,11 @@ import itertools
 import math
 import os
 
+try:
+    import collections.abc as collections_abc
+except ImportError:
+    collections_abc = collections
+
 from pyasn1.codec.der import decoder
 from pyasn1.codec.der import encoder
 from pyasn1.type.univ import Integer
@@ -98,7 +103,7 @@ __all__ = ['SubPackets',
            'ECDHCipherText', ]
 
 
-class SubPackets(collections.MutableMapping, Field):
+class SubPackets(collections_abc.MutableMapping, Field):
     _spmodule = signature
 
     def __init__(self):