python2.pkgs.sphinx: user proper python2 lexer

pkgs/development/python-modules/sphinx/2.nix

@@ -60,6 +60,13 @@ buildPythonPackage rec {
   # Lots of tests. Needs network as well at some point.
   doCheck = false;
 
+  patches = [
+    # Since pygments 2.5, PythonLexer refers to python3. If we want to use
+    # python2, we need to explicitly specify Python2Lexer.
+    # Not upstreamed since there doesn't seem to be any upstream maintenance
+    # branch for 1.8 (and this patch doesn't make any sense for 2.x).
+    ./python2-lexer.patch
+  ];
   # https://github.com/NixOS/nixpkgs/issues/22501
   # Do not run `python sphinx-build arguments` but `sphinx-build arguments`.
   postPatch = ''

pkgs/development/python-modules/sphinx/python2-lexer.patch

@@ -0,0 +1,22 @@
+diff --git a/sphinx/highlighting.py b/sphinx/highlighting.py
+index ac2bd1b06..63ca52de2 100644
+--- a/sphinx/highlighting.py
++++ b/sphinx/highlighting.py
+@@ -16,7 +16,7 @@ from pygments.filters import ErrorToken
+ from pygments.formatters import HtmlFormatter, LatexFormatter
+ from pygments.lexer import Lexer  # NOQA
+ from pygments.lexers import get_lexer_by_name, guess_lexer
+-from pygments.lexers import PythonLexer, Python3Lexer, PythonConsoleLexer, \
++from pygments.lexers import Python2Lexer, Python3Lexer, PythonConsoleLexer, \
+     CLexer, TextLexer, RstLexer
+ from pygments.styles import get_style_by_name
+ from pygments.util import ClassNotFound
+@@ -40,7 +40,7 @@ logger = logging.getLogger(__name__)
+ 
+ lexers = dict(
+     none = TextLexer(stripnl=False),
+-    python = PythonLexer(stripnl=False),
++    python = Python2Lexer(stripnl=False),
+     python3 = Python3Lexer(stripnl=False),
+     pycon = PythonConsoleLexer(stripnl=False),
+     pycon3 = PythonConsoleLexer(python3=True, stripnl=False),