Fix pylint issues in HTTP/2 module

- Add pylint disable comments for global-statement in lazy import pattern
- Remove unnecessary pass statements in error subclasses
- Remove useless return None at end of _handle_request_received methods

gunicorn/http2/__init__.py

@@ -22,7 +22,7 @@ def is_http2_available():
     Returns:
         bool: True if the h2 library is installed with minimum required version.
     """
-    global _h2_available, _h2_version
+    global _h2_available, _h2_version  # pylint: disable=global-statement
 
     if _h2_available is not None:
         return _h2_available

gunicorn/http2/async_connection.py

@@ -30,7 +30,7 @@ _h2_settings = None
 
 def _import_h2():
     """Lazily import h2 library components."""
-    global _h2, _h2_config, _h2_events, _h2_exceptions, _h2_settings
+    global _h2, _h2_config, _h2_events, _h2_exceptions, _h2_settings  # pylint: disable=global-statement
 
     if _h2 is not None:
         return
@@ -215,7 +215,6 @@ class AsyncHTTP2Connection:
 
         # Process headers
         stream.receive_headers(headers, end_stream=False)
-        return None
 
     def _handle_data_received(self, event):
         """Handle DataReceived event."""

gunicorn/http2/connection.py

@@ -29,7 +29,7 @@ _h2_settings = None
 
 def _import_h2():
     """Lazily import h2 library components."""
-    global _h2, _h2_config, _h2_events, _h2_exceptions, _h2_settings
+    global _h2, _h2_config, _h2_events, _h2_exceptions, _h2_settings  # pylint: disable=global-statement
 
     if _h2 is not None:
         return
@@ -203,9 +203,6 @@ class HTTP2ServerConnection:
 
         Args:
             event: RequestReceived event with headers
-
-        Returns:
-            HTTP2Request if stream ended with headers, None otherwise
         """
         stream_id = event.stream_id
         headers = event.headers
@@ -215,12 +212,9 @@ class HTTP2ServerConnection:
         self.streams[stream_id] = stream
 
         # Process headers
+        # The StreamEnded event will come separately for GET/HEAD with no body
         stream.receive_headers(headers, end_stream=False)
 
-        # Check if this was a GET/HEAD with no body
-        # The StreamEnded event will come separately
-        return None
-
     def _handle_data_received(self, event):
         """Handle DataReceived event.
 

gunicorn/http2/errors.py

@@ -114,14 +114,10 @@ class HTTP2StreamError(HTTP2Error):
 class HTTP2ConnectionError(HTTP2Error):
     """Error affecting the entire connection."""
 
-    pass
-
 
 class HTTP2ConfigurationError(HTTP2Error):
     """Invalid HTTP/2 configuration."""
 
-    pass
-
 
 class HTTP2NotAvailable(HTTP2Error):
     """HTTP/2 support is not available (h2 library not installed)."""