No byteswarning

src/h2/events.py

@@ -591,8 +591,8 @@ def __init__(self):
     def __repr__(self):
         return (
             "<AlternativeServiceAvailable origin:%s, field_value:%s>" % (
-                self.origin.decode('utf-8', 'ignore'),
-                self.field_value.decode('utf-8', 'ignore'),
+                (self.origin or b'').decode('utf-8', 'ignore'),
+                (self.field_value or b'').decode('utf-8', 'ignore'),
             )
         )
 

src/h2/stream.py

@@ -25,7 +25,8 @@
 from .utilities import (
     guard_increment_window, is_informational_response, authority_from_headers,
     validate_headers, validate_outbound_headers, normalize_outbound_headers,
-    HeaderValidationFlags, extract_method_header, normalize_inbound_headers
+    HeaderValidationFlags, extract_method_header, normalize_inbound_headers,
+    utf8_encode_headers
 )
 from .windows import WindowManager
 
@@ -851,6 +852,9 @@ def send_headers(self, headers, encoder, end_stream=False):
         # we need to scan the header block to see if this is an informational
         # response.
         input_ = StreamInputs.SEND_HEADERS
+
+        headers = utf8_encode_headers(headers)
+
         if ((not self.state_machine.client) and
                 is_informational_response(headers)):
             if end_stream:
@@ -1240,6 +1244,9 @@ def _build_headers_frames(self,
         """
         Helper method to build headers or push promise frames.
         """
+
+        headers = utf8_encode_headers(headers)
+
         # We need to lowercase the header names, and to ensure that secure
         # header fields are kept out of compression contexts.
         if self.config.normalize_outbound_headers:
@@ -1319,7 +1326,7 @@ def _initialize_content_length(self, headers):
                     self._expected_content_length = int(v, 10)
                 except ValueError:
                     raise ProtocolError(
-                        "Invalid content-length header: %s" % v
+                        f"Invalid content-length header: {repr(v)}"
                     )
 
                 return