Remove more python 2 compatibility code. (#259)

Since python 2.7 is no longer supported.

Author: asherf

docs/conf.py

@@ -1,5 +1,3 @@
-# -*- coding: utf-8 -*-
-#
 # python-jose documentation build configuration file, created by
 # sphinx-quickstart on Thu May  7 13:48:43 2015.
 #

jose/jwe.py

@@ -1,13 +1,9 @@
 import binascii
 import json
 import zlib
+from collections.abc import Mapping
 from struct import pack
 
-try:
-    from collections.abc import Mapping  # Python 3
-except ImportError:
-    from collections import Mapping  # Python 2, will be deprecated in Python 3.8
-
 from . import jwk
 from .backends import get_random_bytes
 from .constants import ALGORITHMS, ZIPS

setup.py

@@ -22,7 +22,7 @@ def get_packages(package):
 
 pyasn1 = ["pyasn1"]
 extras_require = {
-    "cryptography": ["cryptography"],
+    "cryptography": ["cryptography>=3.4.0"],
     "pycrypto": ["pycrypto >=2.6.0, <2.7.0"] + pyasn1,
     "pycryptodome": ["pycryptodome >=3.3.1, <4.0.0"] + pyasn1,
 }