Issue #16301: Fix the localhost verification in urllib/request.py for file://. Modify tests to use localhost for local temp files, which could make Windows Buildbot (#16300) happy

Lib/test/test_urllib.py

@@ -277,7 +277,7 @@ Content-Type: text/html; charset=iso-8859-1
 
     def test_file_notexists(self):
         fd, tmp_file = tempfile.mkstemp()
-        tmp_fileurl = 'file://' + tmp_file
+        tmp_fileurl = 'file://localhost' + tmp_file
 
         self.assertTrue(os.path.exists(tmp_file))
         self.assertTrue(urlopen(tmp_fileurl))

Lib/urllib/request.py

@@ -1905,7 +1905,7 @@ class URLopener:
             return addinfourl(open(localname, 'rb'), headers, urlfile)
         host, port = splitport(host)
         if (not port
-           and socket.gethostbyname(host) in (localhost() + thishost())):
+           and socket.gethostbyname(host) in ((localhost(),) + thishost())):
             urlfile = file
             if file[:1] == '/':
                 urlfile = 'file://' + file

Misc/NEWS

@@ -59,6 +59,9 @@ Core and Builtins
 Library
 -------
 
+- Issue #16301: Fix the localhost verification in urllib/request.py for file://
+  urls.
+
 - Issue #16250: Fix the invocations of URLError which had misplaced filename
   attribute for exception.