Clarify version fetching

tooling/src/hypothesistooling/__main__.py

@@ -308,10 +308,14 @@ def update_python_versions():
 
 def update_pyodide_versions():
     vers_re = r"(\d+\.\d+\.\d+)"
-    pyodide_version = re.findall(
-        f"pyodide_build-{vers_re}-py3-none-any.whl",
-        requests.get("https://pypi.org/simple/pyodide-build/").text,
-    )[-1]
+    pyodide_version = max(
+        # Don't just pick the most recent version; find the highest stable version.
+        re.findall(
+            f"pyodide_build-{vers_re}-py3-none-any.whl",  # excludes pre-releases
+            requests.get("https://pypi.org/simple/pyodide-build/").text,
+        ),
+        key=lambda version: tuple(int(x) for x in version.split(".")),
+    )
     makefile_url = f"https://raw.githubusercontent.com/pyodide/pyodide/{pyodide_version}/Makefile.envs"
     python_version, emscripten_version = re.search(
         rf"export PYVERSION \?= {vers_re}\nexport PYODIDE_EMSCRIPTEN_VERSION \?= {vers_re}\n",
@@ -340,7 +344,8 @@ def update_vendored_files():
     if fname.read_bytes().splitlines()[1:] != new.splitlines()[1:]:
         fname.write_bytes(new)
 
-    # Always require the latest version of the tzdata package
+    # Always require the most recent version of tzdata - we don't need to worry about
+    # pre-releases because tzdata is a 'latest data' package  (unlike pyodide-build).
     tz_url = "https://pypi.org/pypi/tzdata/json"
     tzdata_version = requests.get(tz_url).json()["info"]["version"]
     setup = pathlib.Path(hp.BASE_DIR, "setup.py")