Links cleanup, in particular peps have moved

IPython/core/magics/osm.py

@@ -127,7 +127,7 b' class OSMagics(Magics):'
         Aliases expand Python variables just like system calls using ! or !!
         do: all expressions prefixed with '$' get expanded.  For details of
         the semantic rules, see PEP-215:
-        https://www.python.org/dev/peps/pep-0215/.  This is the library used by
+        https://peps.python.org/pep-0215/.  This is the library used by
         IPython for variable expansion.  If you want to access a true shell
         variable, an extra $ is necessary to prevent its expansion by
         IPython::

docs/source/links.txt

@@ -20,9 +20,6 b''
 .. _ipython: https://ipython.org
 .. _`ipython manual`: https://ipython.org/documentation.html
 .. _ipython_github: http://github.com/ipython/ipython/
-.. _ipython_github_repo: http://github.com/ipython/ipython/
-.. _ipython_downloads: https://ipython.org/download.html
-.. _ipython_pypi: http://pypi.python.org/pypi/ipython
 .. _nbviewer: http://nbviewer.ipython.org
 
 .. _ZeroMQ: http://zeromq.org
@@ -35,8 +32,7 b''
 .. _reST: http://docutils.sourceforge.net/rst.html
 .. _docutils: http://docutils.sourceforge.net
 .. _lyx: http://www.lyx.org
-.. _pep8: http://www.python.org/dev/peps/pep-0008
-.. _numpy_coding_guide: https://github.com/numpy/numpy/blob/master/doc/HOWTO_DOCUMENT.rst.txt
+.. _pep8: https://peps.python.org/pep-0008/
 
 .. Licenses
 .. _GPL: http://www.gnu.org/licenses/gpl.html

docs/source/whatsnew/version6.rst

@@ -277,7 +277,7 b' automatically upgrade to the latest version compatible with your system.'
 
 The ability to use only Python 3 on the code base of IPython brings a number
 of advantages. Most of the newly written code make use of `optional function type
-annotation <https://www.python.org/dev/peps/pep-0484/>`_ leading to clearer code
+annotation <https://peps.python.org/pep-0484/>`_ leading to clearer code
 and better documentation.
 
 The total size of the repository has also decreased by about 1500 lines (for the 

examples/IPython Kernel/Importing Notebooks.ipynb

@@ -15,7 +15,7 b''
     "This is made difficult by the fact that Notebooks are not plain Python files,\n",
     "and thus cannot be imported by the regular Python machinery.\n",
     "\n",
-    "Fortunately, Python provides some fairly sophisticated [hooks](http://www.python.org/dev/peps/pep-0302/) into the import machinery,\n",
+    "Fortunately, Python provides some fairly sophisticated [hooks](https://peps.python.org/pep-0302/) into the import machinery,\n",
     "so we can actually make IPython notebooks importable without much difficulty,\n",
     "and only using public APIs."
    ]