Fix the fromutctimestamp warning on 3.12.

Drop old versions, as generally we build docs using a recent
version.

noxfile.py

@@ -21,7 +21,7 @@ def _session(fn):
     return _session
 
 
-@session(python=["3.8", "3.9", "3.10", "3.11", "3.12", "pypy3"])
+@session(python=["3.11", "3.12"])
 def tests(session):
     session.install("pytest", ROOT)
     session.run("pytest", *session.posargs, PACKAGE)

pyproject.toml

@@ -10,7 +10,7 @@ name = "sphinx_json_schema_spec"
 description = "Sphinx support for the JSON Schema specifications"
 readme = "README.rst"
 license = {text = "MIT"}
-requires-python = ">=3.8"
+requires-python = ">=3.11"
 keywords = ["json schema", "jsonschema", "data validation", "sphinx", "json"]
 authors = [
   {email = "Julian+sphinx-json-schema-spec@GrayVines.com"},
@@ -22,9 +22,6 @@ classifiers = [
   "License :: OSI Approved :: MIT License",
   "Operating System :: OS Independent",
   "Programming Language :: Python",
-  "Programming Language :: Python :: 3.8",
-  "Programming Language :: Python :: 3.9",
-  "Programming Language :: Python :: 3.10",
   "Programming Language :: Python :: 3.11",
   "Programming Language :: Python :: 3.12",
   "Programming Language :: Python :: Implementation :: CPython",

sphinx_json_schema_spec/__init__.py

@@ -2,17 +2,13 @@
 Sphinx support for interlinking to the JSON Schema specifications.
 """
 from contextlib import suppress
-from datetime import datetime
+from datetime import UTC, datetime
+from importlib import metadata
 from pathlib import Path
 from urllib.parse import urljoin
 import ssl
 import urllib.request
 
-try:
-    from importlib import metadata
-except ImportError:
-    import importlib_metadata as metadata  # type: ignore
-
 from docutils import nodes
 from lxml import html
 
@@ -76,7 +72,7 @@ def fetch_or_load(cache_path, url):
     headers = {"User-Agent": f"sphinx-json-schema-spec v{version}"}
 
     with suppress(FileNotFoundError):
-        modified = datetime.utcfromtimestamp(cache_path.stat().st_mtime)
+        modified = datetime.fromtimestamp(cache_path.stat().st_mtime, UTC)
         date = modified.strftime("%a, %d %b %Y %I:%M:%S UTC")
         headers["If-Modified-Since"] = date