bpo-25910: Link redirections in docs (#1933)

Fixes some redirection links in docs.
diff --git a/Doc/howto/logging.rst b/Doc/howto/logging.rst
index 8074b0f..4ee68b4 100644
--- a/Doc/howto/logging.rst
+++ b/Doc/howto/logging.rst
@@ -314,7 +314,7 @@
 If your logging needs are simple, then use the above examples to incorporate
 logging into your own scripts, and if you run into problems or don't
 understand something, please post a question on the comp.lang.python Usenet
-group (available at https://groups.google.com/group/comp.lang.python) and you
+group (available at https://groups.google.com/forum/#!forum/comp.lang.python) and you
 should receive help before too long.
 
 Still here? You can carry on reading the next few sections, which provide a
diff --git a/Doc/howto/pyporting.rst b/Doc/howto/pyporting.rst
index bec6a3d..98c8120 100644
--- a/Doc/howto/pyporting.rst
+++ b/Doc/howto/pyporting.rst
@@ -433,12 +433,12 @@
 .. _Futurize: http://python-future.org/automatic_conversion.html
 .. _importlib: https://docs.python.org/3/library/importlib.html#module-importlib
 .. _importlib2: https://pypi.python.org/pypi/importlib2
-.. _Modernize: https://python-modernize.readthedocs.org/en/latest/
+.. _Modernize: https://python-modernize.readthedocs.io/
 .. _mypy: http://mypy-lang.org/
 .. _Porting to Python 3: http://python3porting.com/
 .. _Pylint: https://pypi.python.org/pypi/pylint
 
-.. _Python 3 Q & A: https://ncoghlan-devs-python-notes.readthedocs.org/en/latest/python3/questions_and_answers.html
+.. _Python 3 Q & A: https://ncoghlan-devs-python-notes.readthedocs.io/en/latest/python3/questions_and_answers.html
 
 .. _pytype: https://github.com/google/pytype
 .. _python-future: http://python-future.org/
diff --git a/Doc/howto/unicode.rst b/Doc/howto/unicode.rst
index a83e5a2..d4b8f8d 100644
--- a/Doc/howto/unicode.rst
+++ b/Doc/howto/unicode.rst
@@ -214,7 +214,7 @@
 origin and development of Unicode is also available on the site.
 
 To help understand the standard, Jukka Korpela has written `an introductory
-guide <https://www.cs.tut.fi/~jkorpela/unicode/guide.html>`_ to reading the
+guide <http://jkorpela.fi/unicode/guide.html>`_ to reading the
 Unicode character tables.
 
 Another `good introductory article <https://www.joelonsoftware.com/2003/10/08/the-absolute-minimum-every-software-developer-absolutely-positively-must-know-about-unicode-and-character-sets-no-excuses/>`_
diff --git a/Doc/howto/urllib2.rst b/Doc/howto/urllib2.rst
index 8d383e0..c1fd5cf 100644
--- a/Doc/howto/urllib2.rst
+++ b/Doc/howto/urllib2.rst
@@ -403,7 +403,7 @@
 :class:`http.client.HTTPMessage` instance.
 
 Typical headers include 'Content-length', 'Content-type', and so on. See the
-`Quick Reference to HTTP Headers <https://www.cs.tut.fi/~jkorpela/http.html>`_
+`Quick Reference to HTTP Headers <http://jkorpela.fi/http.html>`_
 for a useful listing of HTTP headers with brief explanations of their meaning
 and use.