These messages are all "syntax error" (lower case) and appear to be from the bison parsers.
e.g. d4_ce_parser.tab.cc lines 1516:
This seems to alway appear inside code surrounded by ‘#if YYERROR_VERBOSE … #endif' So there might be a parser built that way and causing these meesages
add #define YYERROR_VERBOSE 0 to *.yy files so output is suppressed