Update docs build configuration (#924)

* Use Python 3.11
* Use Sphinx 5 (and update extlinks configuration)
* Use Python 3 intersphinx mapping
* Install Babel from the build directory

Refs #920

.readthedocs.yml

@@ -3,10 +3,17 @@
 version: 2
 
 build:
-  os: ubuntu-20.04
+  os: ubuntu-22.04
   tools:
-    python: "3.9"
-
+    python: "3.11"
+  jobs:
+    pre_build:
+      # Replace any Babel version something may have pulled in
+      # with the copy we're working on.  We'll also need to build
+      # the data files at that point, or date formatting _within_
+      # Sphinx will fail.
+      - pip install -e .
+      - make import-cldr
 sphinx:
    configuration: docs/conf.py
 

docs/conf.py

@@ -251,10 +251,10 @@
 #texinfo_show_urls = 'footnote'
 
 intersphinx_mapping = {
-    'https://docs.python.org/2/': None,
+    'https://docs.python.org/3/': None,
 }
 
 extlinks = {
-    'gh': ('https://github.com/python-babel/babel/issues/%s', '#'),
-    'trac': ('http://babel.edgewall.org/ticket/%s', 'ticket #'),
+    'gh': ('https://github.com/python-babel/babel/issues/%s', '#%s'),
+    'trac': ('http://babel.edgewall.org/ticket/%s', 'ticket #%s'),
 }

docs/requirements.txt

@@ -1 +1 @@
-Sphinx~=4.4.0
+Sphinx~=5.3.0