[3.13] pythongh-134262: increase retries in Tools/build/generate_sbom.py (pythonGH-134558)

(cherry picked from commit 3f9eb55)

Co-authored-by: Emma Smith <emma@emmatyping.dev>

Author: emmatyping

Tools/build/generate_sbom.py

@@ -1,13 +1,16 @@
 """Tool for generating Software Bill of Materials (SBOM) for Python's dependencies"""
 import os
+import random
 import re
 import hashlib
 import json
 import glob
 from pathlib import Path, PurePosixPath, PureWindowsPath
 import subprocess
 import sys
+import urllib.error
 import urllib.request
+import time
 import typing
 
 CPYTHON_ROOT_DIR = Path(__file__).parent.parent.parent
@@ -163,6 +166,23 @@ def get_externals() -> list[str]:
     return externals
 
 
+def download_with_retries(download_location: str,
+                          max_retries: int = 7,
+                          base_delay: float = 2.25,
+                          max_jitter: float = 1.0) -> typing.Any:
+    """Download a file with exponential backoff retry."""
+    for attempt in range(max_retries):
+        try:
+            resp = urllib.request.urlopen(download_location)
+        except urllib.error.URLError as ex:
+            if attempt == max_retries:
+                msg = f"Download from {download_location} failed."
+                raise OSError(msg) from ex
+            time.sleep(base_delay**attempt + random.uniform(0, max_jitter))
+        else:
+            return resp
+
+
 def check_sbom_packages(sbom_data: dict[str, typing.Any]) -> None:
     """Make a bunch of assertions about the SBOM package data to ensure it's consistent."""