Explicitly use proxy

server.py

@@ -52,6 +52,9 @@ app = fastapi.FastAPI(
     root_path=os.environ.get("PREVIEW_ROOT_PATH", ""),
     lifespan=startup
 )
+proxy = os.getenv("PREVIEW_PROXY")
+if proxy:
+    logging.debug("Using proxy: %r", proxy)
 lock = Lock()
 # noinspection PyTypeChecker
 app.add_middleware(
@@ -259,7 +262,8 @@ def preview_url(
             },
             timeout=60,
             follow_redirects=False,
-            trust_env=True  # for HTTP[S]/ALL_PROXY environment variables.
+            trust_env=True,  # for HTTP[S]/ALL_PROXY environment variables.
+            proxy=proxy
         ) as client:
             try:
                 response = client.get(