https://bugs.gentoo.org/792558

From 83407ffc7acc00cc025b9f6ed063add9ab9f9bcc Mon Sep 17 00:00:00 2001
From: Krzysztof Gogolewski <krzysztof.gogolewski@tweag.io>
Date: Fri, 25 Sep 2020 02:52:19 +0200
Subject: [PATCH] Various documentation fixes

* Use r'' in conf.py. This fixes a Sphinx warning:
  WARNING: Support for evaluating Python 2 syntax is deprecated and will be removed in Sphinx 4.0. Convert docs/users_guide/conf.py to Python 3 syntax.
--- a/docs/users_guide/conf.py
+++ b/docs/users_guide/conf.py
@@ -100,13 +100,13 @@ htmlhelp_basename = 'GHCUsersGuide'
 latex_elements = {
     'inputenc': '',
     'utf8extra': '',
-    'preamble': '''
+    'preamble': r'''
 \usepackage{fontspec}
 \usepackage{makeidx}
 \setsansfont{DejaVu Sans}
 \setromanfont{DejaVu Serif}
 \setmonofont{DejaVu Sans Mono}
-\setlength{\\tymin}{45pt}
+\setlength{\tymin}{45pt}
 ''',
 }