Improve highlighting of some code blocks. (GH-6401)

(cherry picked from commit 46936d5a71d1683dbd8ddb6d7f39aab50ecfec50)

Co-authored-by: Serhiy Storchaka <storchaka@gmail.com>
diff --git a/Doc/extending/embedding.rst b/Doc/extending/embedding.rst
index ab2f616..7e4fc19 100644
--- a/Doc/extending/embedding.rst
+++ b/Doc/extending/embedding.rst
@@ -323,7 +323,7 @@
 programmatically extract the configuration values that you will want to
 combine together.  For example:
 
-.. code-block:: python
+.. code-block:: pycon
 
    >>> import sysconfig
    >>> sysconfig.get_config_var('LIBS')
diff --git a/Doc/extending/extending.rst b/Doc/extending/extending.rst
index e02f783..82b689e 100644
--- a/Doc/extending/extending.rst
+++ b/Doc/extending/extending.rst
@@ -43,7 +43,9 @@
 Python fans...) and let's say we want to create a Python interface to the C
 library function :c:func:`system` [#]_. This function takes a null-terminated
 character string as argument and returns an integer.  We want this function to
-be callable from Python as follows::
+be callable from Python as follows:
+
+.. code-block:: pycon
 
    >>> import spam
    >>> status = spam.system("ls -l")
@@ -439,7 +441,9 @@
 and rebuild the interpreter.  Luckily, this is very simple on Unix: just place
 your file (:file:`spammodule.c` for example) in the :file:`Modules/` directory
 of an unpacked source distribution, add a line to the file
-:file:`Modules/Setup.local` describing your file::
+:file:`Modules/Setup.local` describing your file:
+
+.. code-block:: sh
 
    spam spammodule.o
 
@@ -450,7 +454,9 @@
 :file:`Setup` file.)
 
 If your module requires additional libraries to link with, these can be listed
-on the line in the configuration file as well, for instance::
+on the line in the configuration file as well, for instance:
+
+.. code-block:: sh
 
    spam spammodule.o -lX11
 
diff --git a/Doc/extending/newtypes_tutorial.rst b/Doc/extending/newtypes_tutorial.rst
index 5e05cf6..ac48637 100644
--- a/Doc/extending/newtypes_tutorial.rst
+++ b/Doc/extending/newtypes_tutorial.rst
@@ -117,7 +117,7 @@
 The name of our type.  This will appear in the default textual representation of
 our objects and in some error messages, for example:
 
-.. code-block:: python
+.. code-block:: pycon
 
    >>> "" + custom.Custom()
    Traceback (most recent call last):
@@ -183,7 +183,7 @@
 This adds the type to the module dictionary.  This allows us to create
 :class:`Custom` instances by calling the :class:`Custom` class:
 
-.. code-block:: python
+.. code-block:: pycon
 
    >>> import custom
    >>> mycustom = custom.Custom()
@@ -655,7 +655,7 @@
 can identify unneeded objects even when their reference counts are not zero.
 This can happen when objects are involved in cycles.  For example, consider:
 
-.. code-block:: python
+.. code-block:: pycon
 
    >>> l = []
    >>> l.append(l)
@@ -672,7 +672,7 @@
 :class:`Custom`, and subclasses may add arbitrary attributes.  For any of
 those two reasons, :class:`Custom` objects can participate in cycles:
 
-.. code-block:: python
+.. code-block:: pycon
 
    >>> import custom3
    >>> class Derived(custom3.Custom): pass
@@ -796,7 +796,7 @@
 regular lists, but will have an additional :meth:`increment` method that
 increases an internal counter:
 
-.. code-block:: python
+.. code-block:: pycon
 
    >>> import sublist
    >>> s = sublist.SubList(range(3))