scripts/dl_github_archive.py: convert to Python 3 with 2-to-3

Let's convert the script to Python 3.

Signed-off-by: Petr Štetiar <ynezz@true.cz>

scripts/dl_github_archive.py

@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 # Copyright (c) 2018 Yousong Zhou <yszhou4tech@gmail.com>
 #
@@ -20,7 +20,7 @@ import ssl
 import subprocess
 import sys
 import time
-import urllib2
+import urllib.request
 
 TMPDIR = os.environ.get('TMP_DIR') or '/tmp'
 TMPDIR_DL = os.path.join(TMPDIR, 'dl')
@@ -194,7 +194,7 @@ class GitHubCommitTsCache(object):
             self.cache[k] = (ts, updated)
 
     def _cache_flush(self, fout):
-        cache = sorted(self.cache.iteritems(), cmp=lambda a, b: b[1][1] - a[1][1])
+        cache = sorted(self.cache.items(), key=lambda a: a[1][1])
         cache = cache[:self.__cachen]
         self.cache = {}
         os.ftruncate(fout.fileno(), 0)
@@ -397,9 +397,9 @@ class DownloadGitHubTarball(object):
             'Accept': 'application/vnd.github.v3+json',
             'User-Agent': 'OpenWrt',
         }
-        req = urllib2.Request(url, headers=headers)
+        req = urllib.request.Request(url, headers=headers)
         sslcontext = ssl._create_unverified_context()
-        fileobj = urllib2.urlopen(req, context=sslcontext)
+        fileobj = urllib.request.urlopen(req, context=sslcontext)
         return fileobj
 
     def _error(self, msg):