whatsnew: cp273 codec (#10907797)

Also updated the docs and added the aliases mentioned by the
references.

Doc/library/codecs.rst

@@ -971,6 +971,10 @@ particular, the following variants typically exist:
 +-----------------+--------------------------------+--------------------------------+
 | cp037           | IBM037, IBM039                 | English                        |
 +-----------------+--------------------------------+--------------------------------+
+| cp273           | 273, IBM273, csIBM273          | German                         |
+|                 |                                |                                |
+|                 |                                | .. versionadded:: 3.4          |
++-----------------+--------------------------------+--------------------------------+
 | cp424           | EBCDIC-CP-HE, IBM424           | Hebrew                         |
 +-----------------+--------------------------------+--------------------------------+
 | cp437           | 437, IBM437                    | English                        |

Doc/whatsnew/3.4.rst

@@ -365,6 +365,9 @@ Some smaller changes made to the core Python language are:
   Contributed by Victor Stinner, Kang-Hao (Kenny) Lu and Serhiy Storchaka in
   :issue:`12892`.
 
+* New EBCDIC :ref:`codec <standard-encodings>` ``cp273``.  (Contributed by
+  Michael Bierenfeld and Andrew Kuchling in :issue:`1097797`.)
+
 * :class:`bytes`.join() and :class:`bytearray`.join() now accept arbitrary
   buffer objects as arguments.  (Contributed by Antoine Pitrou in
   :issue:`15958`.)

Lib/encodings/aliases.py

@@ -109,6 +109,11 @@ aliases = {
     '1258'               : 'cp1258',
     'windows_1258'       : 'cp1258',
 
+    # cp273 codec
+    '273'                : 'cp273',
+    'ibm273'             : 'cp273',
+    'csibm273'           : 'cp273',
+
     # cp424 codec
     '424'                : 'cp424',
     'csibm424'           : 'cp424',