Links to Python 3 docs in the warning header on Python 2.7 docs go to 404 pages when the library was removed in Python 3

[verhovsky]

Describe the bug
There are a number of HTML files that were moved between the Python 2.7 and Python 3 documentation websites (because some libraries were moved, renamed and removed). The documentation for Python 2.7 contains a banner with a link to the current page with the "/2/" in the URL changed to "/3/". For the libraries that are missing from Python 3, these links open a 404 page.

To Reproduce

1. Go to https://docs.python.org/2/library/stringio.html
2. Click on "You should upgrade and read the Python documentation for the current stable release." at the very top.
3. See a "404 Not Found" error

Expected behavior
Either (in order of preference)

• redirect to https://docs.python.org/3/library/io.html#io.StringIO
• redirect to https://docs.python.org/3/library/io.html
• redirect to https://docs.python.org (the docs homepage)
• make the text "Python documentation for the current stable release" regular text instead of a link

Additional context
These are the files that are missing between Python 2.7 and Python 3.8 along with where (I think) they should be redirected to:

Python 2	Python 3
https://docs.python.org/2/library/fpformat.html
https://docs.python.org/2/library/mutex.html
https://docs.python.org/2/library/new.html
https://docs.python.org/2/library/statvfs.html
https://docs.python.org/2/library/dircache.html
https://docs.python.org/2/library/macpath.html
https://docs.python.org/2/library/dbhash.html
https://docs.python.org/2/library/bsddb.html
https://docs.python.org/2/library/someos.html
https://docs.python.org/2/library/popen2.html
https://docs.python.org/2/library/mhlib.html
https://docs.python.org/2/library/mimetools.html
https://docs.python.org/2/library/mimewriter.html
https://docs.python.org/2/library/mimify.html
https://docs.python.org/2/library/multifile.html
https://docs.python.org/2/library/sgmllib.html
https://docs.python.org/2/library/imageop.html
https://docs.python.org/2/library/hotshot.html
https://docs.python.org/2/library/future_builtins.html
https://docs.python.org/2/library/user.html
https://docs.python.org/2/library/fpectl.html
https://docs.python.org/2/library/restricted.html
https://docs.python.org/2/library/rexec.html
https://docs.python.org/2/library/bastion.html
https://docs.python.org/2/library/imputil.html
https://docs.python.org/2/library/compiler.html
https://docs.python.org/2/library/dl.html
https://docs.python.org/2/library/posixfile.html
https://docs.python.org/2/library/commands.html
https://docs.python.org/2/library/mac.html
https://docs.python.org/2/library/ic.html
https://docs.python.org/2/library/macos.html
https://docs.python.org/2/library/macostools.html
https://docs.python.org/2/library/easydialogs.html
https://docs.python.org/2/library/framework.html
https://docs.python.org/2/library/autogil.html
https://docs.python.org/2/library/carbon.html
https://docs.python.org/2/library/colorpicker.html
https://docs.python.org/2/library/macosa.html
https://docs.python.org/2/library/gensuitemodule.html
https://docs.python.org/2/library/aetools.html
https://docs.python.org/2/library/aepack.html
https://docs.python.org/2/library/aetypes.html
https://docs.python.org/2/library/miniaeframe.html
https://docs.python.org/2/library/sgi.html
https://docs.python.org/2/library/al.html
https://docs.python.org/2/library/cd.html
https://docs.python.org/2/library/fl.html
https://docs.python.org/2/library/fm.html
https://docs.python.org/2/library/gl.html
https://docs.python.org/2/library/imgfile.html
https://docs.python.org/2/library/jpeg.html
https://docs.python.org/2/library/sun.html
https://docs.python.org/2/library/sunaudio.html
https://docs.python.org/2/c-api/int.html
https://docs.python.org/2/c-api/string.html
https://docs.python.org/2/c-api/class.html
https://docs.python.org/2/c-api/cobject.html
https://docs.python.org/2/howto/doanddont.html
https://docs.python.org/2/howto/webservers.html
https://docs.python.org/2/library/strings.html	https://docs.python.org/3/library/text.html
https://docs.python.org/2/library/stringio.html	https://docs.python.org/3/library/io.html#io.StringIO
https://docs.python.org/2/library/sets.html	https://docs.python.org/3/library/stdtypes.html#set
https://docs.python.org/2/library/userdict.html	https://docs.python.org/3/library/collections.html#userdict-objects
https://docs.python.org/2/library/repr.html	https://docs.python.org/3/library/reprlib.html
https://docs.python.org/2/library/copy_reg.html	https://docs.python.org/3/library/copyreg.html
https://docs.python.org/2/library/anydbm.html	https://docs.python.org/3/library/dbm.html
https://docs.python.org/2/library/whichdb.html	https://docs.python.org/3/library/dbm.html#dbm.whichdb
https://docs.python.org/2/library/dumbdbm.html	https://docs.python.org/3/library/dbm.html#module-dbm.dumb
https://docs.python.org/2/library/dbm.html	https://docs.python.org/3/library/dbm.html#module-dbm.ndbm
https://docs.python.org/2/library/gdbm.html	https://docs.python.org/3/library/dbm.html#module-dbm.gnu
https://docs.python.org/2/library/robotparser.html	https://docs.python.org/3/library/urllib.robotparser.html
https://docs.python.org/2/library/md5.html	https://docs.python.org/3/library/hashlib.html
https://docs.python.org/2/library/sha.html	https://docs.python.org/3/library/hashlib.html
https://docs.python.org/2/library/thread.html	https://docs.python.org/3/library/_thread.html
https://docs.python.org/2/library/dummy_thread.html	https://docs.python.org/3/library/_dummy_thread.html
https://docs.python.org/2/library/email-examples.html	https://docs.python.org/3/library/email.examples.html
https://docs.python.org/2/library/rfc822.html
https://docs.python.org/2/library/htmlparser.html	https://docs.python.org/3/library/html.parser.html
https://docs.python.org/2/library/htmllib.html
https://docs.python.org/2/library/urllib2.html	https://docs.python.org/3/library/urllib.request.html
https://docs.python.org/2/library/httplib.html	https://docs.python.org/3/library/http.client.html
https://docs.python.org/2/library/urlparse.html	https://docs.python.org/3/library/urllib.parse.html
https://docs.python.org/2/library/basehttpserver.html	https://docs.python.org/3/library/http.server.html
https://docs.python.org/2/library/simplehttpserver.html	https://docs.python.org/3/library/http.server.html
https://docs.python.org/2/library/cgihttpserver.html	https://docs.python.org/3/library/http.server.html#http.server.CGIHTTPRequestHandler
https://docs.python.org/2/library/cookielib.html	https://docs.python.org/3/library/http.cookiejar.html
https://docs.python.org/2/library/cookie.html	https://docs.python.org/3/library/http.cookies.html
https://docs.python.org/2/library/xmlrpclib.html	https://docs.python.org/3/library/xmlrpc.client.html
https://docs.python.org/2/library/simplexmlrpcserver.html	https://docs.python.org/3/library/xmlrpc.server.html
https://docs.python.org/2/library/docxmlrpcserver.html	https://docs.python.org/3/library/xmlrpc.server.html
https://docs.python.org/2/library/ttk.html	https://docs.python.org/3/library/tkinter.ttk.html
https://docs.python.org/2/library/tix.html	https://docs.python.org/3/library/tkinter.tix.html
https://docs.python.org/2/library/scrolledtext.html	https://docs.python.org/3/library/tkinter.scrolledtext.html
https://docs.python.org/2/library/__builtin__.html	https://docs.python.org/3/library/builtins.html
https://docs.python.org/2/library/_winreg.html	https://docs.python.org/3/library/winreg.html

Code to generate the above table (I added some alternatives in comments - for example to libraries that replace the functionality of the removed package):

redirects = {
    "library/fpformat.html": None,
    "library/mutex.html": None,
    "library/new.html": None,
    "library/statvfs.html": None,
    "library/dircache.html": None,
    "library/macpath.html": None,
    "library/dbhash.html": None,
    "library/bsddb.html": None,
    # "library/someos.html": "library/index.html",
    "library/someos.html": None,
    # "library/popen2.html": "library/subprocess.html",
    "library/popen2.html": None,
    # "library/mhlib.html": "library/mailbox.html",
    "library/mhlib.html": None,
    # "library/mimetools.html": "library/email.html",
    "library/mimetools.html": None,
    # "library/mimewriter.html": "library/email.html",
    "library/mimewriter.html": None,
    # "library/mimify.html": "library/email.html",
    "library/mimify.html": None,
    # "library/multifile.html": "library/email.html",
    "library/multifile.html": None,
    "library/sgmllib.html": None,
    "library/imageop.html": None,
    # "library/hotshot.html": "library/profile.html",
    "library/hotshot.html": None,
    "library/future_builtins.html": None,
    "library/user.html": None,
    "library/fpectl.html": None,
    "library/restricted.html": None,
    "library/rexec.html": None,
    "library/bastion.html": None,
    "library/imputil.html": None,
    "library/compiler.html": None,
    "library/dl.html": None,
    "library/posixfile.html": None,
    # "library/commands.html": "library/subprocess.html",
    "library/commands.html": None,
    "library/mac.html": None,
    "library/ic.html": None,
    "library/macos.html": None,
    "library/macostools.html": None,
    "library/easydialogs.html": None,
    "library/framework.html": None,
    "library/autogil.html": None,
    "library/carbon.html": None,
    "library/colorpicker.html": None,
    "library/macosa.html": None,
    "library/gensuitemodule.html": None,
    "library/aetools.html": None,
    "library/aepack.html": None,
    "library/aetypes.html": None,
    "library/miniaeframe.html": None,
    "library/sgi.html": None,
    "library/al.html": None,
    "library/cd.html": None,
    "library/fl.html": None,
    "library/fm.html": None,
    "library/gl.html": None,
    "library/imgfile.html": None,
    "library/jpeg.html": None,
    "library/sun.html": None,
    "library/sunaudio.html": None,
    # "c-api/int.html": "c-api/long.html",
    "c-api/int.html": None,
    "c-api/string.html": None,
    "c-api/class.html": None,
    "c-api/cobject.html": None,
    "howto/doanddont.html": None,
    "howto/webservers.html": None,
    # "library/strings.html": None,
    "library/strings.html": "library/text.html",
    "library/stringio.html": "library/io.html#io.StringIO",
    "library/sets.html": "library/stdtypes.html#set",
    "library/userdict.html": "library/collections.html#userdict-objects",
    "library/repr.html": "library/reprlib.html",
    "library/copy_reg.html": "library/copyreg.html",
    "library/anydbm.html": "library/dbm.html",
    "library/whichdb.html": "library/dbm.html#dbm.whichdb",
    "library/dumbdbm.html": "library/dbm.html#module-dbm.dumb",
    "library/dbm.html": "library/dbm.html#module-dbm.ndbm",
    "library/gdbm.html": "library/dbm.html#module-dbm.gnu",
    "library/robotparser.html": "library/urllib.robotparser.html",
    "library/md5.html": "library/hashlib.html",
    "library/sha.html": "library/hashlib.html",
    "library/thread.html": "library/_thread.html",
    "library/dummy_thread.html": "library/_dummy_thread.html",
    "library/email-examples.html": "library/email.examples.html",
    "library/rfc822.html": None,
    "library/htmlparser.html": "library/html.parser.html",
    "library/htmllib.html": None,
    "library/urllib2.html": "library/urllib.request.html",
    "library/httplib.html": "library/http.client.html",
    "library/urlparse.html": "library/urllib.parse.html",
    "library/basehttpserver.html": "library/http.server.html",
    "library/simplehttpserver.html": "library/http.server.html",
    "library/cgihttpserver.html": "library/http.server.html#http.server.CGIHTTPRequestHandler",
    "library/cookielib.html": "library/http.cookiejar.html",
    "library/cookie.html": "library/http.cookies.html",
    "library/xmlrpclib.html": "library/xmlrpc.client.html",
    "library/simplexmlrpcserver.html": "library/xmlrpc.server.html",
    "library/docxmlrpcserver.html": "library/xmlrpc.server.html",
    "library/ttk.html": "library/tkinter.ttk.html",
    "library/tix.html": "library/tkinter.tix.html",
    "library/scrolledtext.html": "library/tkinter.scrolledtext.html",
    "library/__builtin__.html": "library/builtins.html",
    "library/_winreg.html": "library/winreg.html",
}

from tabulate import tabulate

print(
    tabulate(
        [
            (
                f"https://docs.python.org/2/{old}",
                "" if new is None else f"https://docs.python.org/3/{new}",
            )
            for old, new in redirects.items()
        ],
        headers=["Python 2", "Python 3"],
        tablefmt="github",
    )
)

See https://github.com/verhovsky/py3redirect/blob/master/special-cases.js for context.

[verhovsky]

Should I open this on bugs.python.org instead? The code that does this is in the CPython repo python/cpython@46ed90d

[Mariatta]

Yes, this should be filed on bugs.python.org. Thanks.