gh-86986: Drop compatibility support for Sphinx 2 (GH-93737)

* Revert "bpo-42843: Keep Sphinx 1.8 and Sphinx 2 compatibility (GH-24282)"

This reverts commit 5c1f15b

* Revert "bpo-42579: Make workaround for various versions of Sphinx more robust (GH-23662)"

This reverts commit b63a620.
(cherry picked from commit 0efe3a1)

Co-authored-by: Adam Turner <9087854+AA-Turner@users.noreply.github.com>

Author: miss-islington

Doc/conf.py

@@ -239,5 +239,3 @@
 # bpo-40204: Disable warnings on Sphinx 2 syntax of the C domain since the
 # documentation is built with -W (warnings treated as errors).
 c_warn_on_allowed_pre_v3 = False
-
-strip_signature_backslash = True

Doc/library/asyncio-stream.rst

@@ -192,7 +192,7 @@ StreamReader
       can be read.  Use the :attr:`IncompleteReadError.partial`
       attribute to get the partially read data.
 
-   .. coroutinemethod:: readuntil(separator=b'\\n')
+   .. coroutinemethod:: readuntil(separator=b'\n')
 
       Read data from the stream until *separator* is found.
 

Doc/library/base64.rst

@@ -199,7 +199,7 @@ The modern interface provides:
    .. versionadded:: 3.4
 
 
-.. function:: a85decode(b, *, foldspaces=False, adobe=False, ignorechars=b' \\t\\n\\r\\v')
+.. function:: a85decode(b, *, foldspaces=False, adobe=False, ignorechars=b' \t\n\r\v')
 
    Decode the Ascii85 encoded :term:`bytes-like object` or ASCII string *b* and
    return the decoded :class:`bytes`.

Doc/library/difflib.rst

@@ -149,7 +149,7 @@ diffs. For comparing directories and files, see also, the :mod:`filecmp` module.
    contains a good example of its use.
 
 
-.. function:: context_diff(a, b, fromfile='', tofile='', fromfiledate='', tofiledate='', n=3, lineterm='\\n')
+.. function:: context_diff(a, b, fromfile='', tofile='', fromfiledate='', tofiledate='', n=3, lineterm='\n')
 
    Compare *a* and *b* (lists of strings); return a delta (a :term:`generator`
    generating the delta lines) in context diff format.
@@ -279,7 +279,7 @@ diffs. For comparing directories and files, see also, the :mod:`filecmp` module.
       emu
 
 
-.. function:: unified_diff(a, b, fromfile='', tofile='', fromfiledate='', tofiledate='', n=3, lineterm='\\n')
+.. function:: unified_diff(a, b, fromfile='', tofile='', fromfiledate='', tofiledate='', n=3, lineterm='\n')
 
    Compare *a* and *b* (lists of strings); return a delta (a :term:`generator`
    generating the delta lines) in unified diff format.
@@ -321,7 +321,7 @@ diffs. For comparing directories and files, see also, the :mod:`filecmp` module.
 
    See :ref:`difflib-interface` for a more detailed example.
 
-.. function:: diff_bytes(dfunc, a, b, fromfile=b'', tofile=b'', fromfiledate=b'', tofiledate=b'', n=3, lineterm=b'\\n')
+.. function:: diff_bytes(dfunc, a, b, fromfile=b'', tofile=b'', fromfiledate=b'', tofiledate=b'', n=3, lineterm=b'\n')
 
    Compare *a* and *b* (lists of bytes objects) using *dfunc*; yield a
    sequence of delta lines (also bytes) in the format returned by *dfunc*.

Doc/library/email.header.rst

@@ -116,7 +116,7 @@ Here is the :class:`Header` class description:
       if *s* is a byte string.
 
 
-   .. method:: encode(splitchars=';, \\t', maxlinelen=None, linesep='\\n')
+   .. method:: encode(splitchars=';, \t', maxlinelen=None, linesep='\n')
 
       Encode a message header into an RFC-compliant format, possibly wrapping
       long lines and encapsulating non-ASCII parts in base64 or quoted-printable

Doc/library/functions.rst

@@ -1387,7 +1387,7 @@ are always available.  They are listed here in alphabetical order.
       supported.
 
 
-.. function:: print(*objects, sep=' ', end='\\n', file=sys.stdout, flush=False)
+.. function:: print(*objects, sep=' ', end='\n', file=sys.stdout, flush=False)
 
    Print *objects* to the text stream *file*, separated by *sep* and followed
    by *end*.  *sep*, *end*, *file*, and *flush*, if present, must be given as keyword

Doc/library/http.cookies.rst

@@ -93,7 +93,7 @@ Cookie Objects
    :meth:`value_decode` are inverses on the range of *value_decode*.
 
 
-.. method:: BaseCookie.output(attrs=None, header='Set-Cookie:', sep='\\r\\n')
+.. method:: BaseCookie.output(attrs=None, header='Set-Cookie:', sep='\r\n')
 
    Return a string representation suitable to be sent as HTTP headers. *attrs* and
    *header* are sent to each :class:`Morsel`'s :meth:`output` method. *sep* is used

Doc/library/io.rst

@@ -1035,7 +1035,7 @@ Text I/O
       .. versionadded:: 3.7
 
 
-.. class:: StringIO(initial_value='', newline='\\n')
+.. class:: StringIO(initial_value='', newline='\n')
 
    A text stream using an in-memory text buffer.  It inherits
    :class:`TextIOBase`.

Doc/library/xml.dom.minidom.rst

@@ -180,7 +180,7 @@ module documentation.  This section lists the differences between the API and
    .. versionchanged:: 3.9
       The *standalone* parameter was added.
 
-.. method:: Node.toprettyxml(indent="\\t", newl="\\n", encoding=None, \
+.. method:: Node.toprettyxml(indent="\t", newl="\n", encoding=None, \
                              standalone=None)
 
    Return a pretty-printed version of the document. *indent* specifies the

Doc/tools/extensions/pyspecific.py

@@ -418,12 +418,7 @@ def run(self):
                                    translatable=False)
             node.append(para)
         env = self.state.document.settings.env
-        # deprecated pre-Sphinx-2 method
-        if hasattr(env, 'note_versionchange'):
-            env.note_versionchange('deprecated', version[0], node, self.lineno)
-        # new method
-        else:
-            env.get_domain('changeset').note_changeset(node)
+        env.get_domain('changeset').note_changeset(node)
         return [node] + messages