Still support <0.6.3

Author: Kludex

uvicorn/protocols/http/httptools_impl.py

@@ -58,7 +58,14 @@ def __init__(
         self.access_logger = logging.getLogger("uvicorn.access")
         self.access_log = self.access_logger.hasHandlers()
         self.parser = httptools.HttpRequestParser(self)
-        self.parser.set_dangerous_leniencies(lenient_data_after_close=True)
+
+        try:
+            # Enable dangerous leniencies to allow server to a response on the first request from a pipelined request.
+            self.parser.set_dangerous_leniencies(lenient_data_after_close=True)
+        except AttributeError:
+            # httptools < 0.6.3
+            pass
+
         self.ws_protocol_class = config.ws_protocol_class
         self.root_path = config.root_path
         self.limit_concurrency = config.limit_concurrency