/usr/include/pion/ is in libpion-net-dev 4.0.7+dfsg-3.1ubuntu4.
This file is owned by root:root, with mode 0o755.
..
/usr/include/pion/net/
/usr/include/pion/net/HTTPAuth.hpp
/usr/include/pion/net/HTTPBasicAuth.hpp
/usr/include/pion/net/HTTPCookieAuth.hpp
/usr/include/pion/net/HTTPMessage.hpp
/usr/include/pion/net/HTTPParser.hpp
/usr/include/pion/net/HTTPReader.hpp
/usr/include/pion/net/HTTPRequest.hpp
/usr/include/pion/net/HTTPRequestReader.hpp
/usr/include/pion/net/HTTPRequestWriter.hpp
/usr/include/pion/net/HTTPResponse.hpp
/usr/include/pion/net/HTTPResponseReader.hpp
/usr/include/pion/net/HTTPResponseWriter.hpp
/usr/include/pion/net/HTTPServer.hpp
/usr/include/pion/net/HTTPTypes.hpp
/usr/include/pion/net/HTTPWriter.hpp
/usr/include/pion/net/PionUser.hpp
/usr/include/pion/net/TCPConnection.hpp
/usr/include/pion/net/TCPServer.hpp
/usr/include/pion/net/TCPStream.hpp
/usr/include/pion/net/TCPTimer.hpp
/usr/include/pion/net/WebServer.hpp
/usr/include/pion/net/WebService.hpp