qapi: Fix crash on stray double quote character

When the lexer chokes on a stray character, its shows the characters
until the next structural character in the error message.  It uses a
regular expression to match a non-empty string of non-structural
characters.  Bug: the regular expression treats '"' as structural.
When the lexer chokes on '"', the match fails, and trips
must_match()'s assertion.  Fix the regular expression.

Fixes: 14c3279 (qapi: Improve reporting of lexical errors)
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <20230428105429.1687850-4-armbru@redhat.com>
Reviewed-by: Juan Quintela <quintela@redhat.com>

scripts/qapi/parser.py

@@ -346,7 +346,7 @@ def accept(self, skip_comment: bool = True) -> None:
             elif not self.tok.isspace():
                 # Show up to next structural, whitespace or quote
                 # character
-                match = must_match('[^[\\]{}:,\\s\'"]+',
+                match = must_match('[^[\\]{}:,\\s\']+',
                                    self.src[self.cursor-1:])
                 raise QAPIParseError(self, "stray '%s'" % match.group(0))