Use surrogateescape to encode headers on websockets implementation

tests/protocols/test_websocket.py

@@ -139,10 +139,13 @@ async def websocket_connect(self, message):
             headers = self.scope.get("headers")
             headers = dict(headers)
             assert headers[b"host"].startswith(b"127.0.0.1")
+            assert headers[b"username"] == bytes("abraão", "utf-8")
             await self.send({"type": "websocket.accept"})
 
     async def open_connection(url):
-        async with websockets.connect(url) as websocket:
+        async with websockets.connect(
+            url, extra_headers=[("username", "abraão")]
+        ) as websocket:
             return websocket.open
 
     config = Config(app=App, ws=protocol_cls, lifespan="off")

uvicorn/protocols/websockets/websockets_impl.py

@@ -99,7 +99,7 @@ async def process_request(self, path, headers):
             subprotocols.extend([token.strip() for token in header.split(",")])
 
         asgi_headers = [
-            (name.encode("ascii"), value.encode("ascii"))
+            (name.encode("ascii"), value.encode("ascii", errors="surrogateescape"))
             for name, value in headers.raw_items()
         ]