fix: Create default SSL context in main thread before downloading inventories

Issue-796: https://github.com/mkdocstrings/mkdocstrings/issue/796
PR-797: #797

Author: ckutlu

src/mkdocstrings/_internal/handlers/base.py

@@ -7,6 +7,7 @@
 import datetime
 import importlib
 import inspect
+import ssl
 import sys
 from concurrent import futures
 from io import BytesIO
@@ -753,6 +754,11 @@ def _download_inventories(self) -> None:
             to_download.extend((handler, url, conf) for url, conf in inv_configs)
 
         if to_download:
+            # YORE: EOL 3.12: Remove block.
+            # NOTE: Create context in main thread to fix issue
+            # https://github.com/mkdocstrings/mkdocstrings/issues/796.
+            _ = ssl.create_default_context()
+
             thread_pool = futures.ThreadPoolExecutor(4)
             for handler, url, conf in to_download:
                 _logger.debug("Downloading inventory from %s", url)