qapi: Improve error message for description following section

The error message is bad when the section is untagged.  For instance,
test case doc-interleaved-section produces "'@foobar:' can't follow
'Note' section", which is okay, but if we drop the "Note:" tag, we get
"'@foobar:' can't follow 'None' section, which is bad.

Change the error message to "description of '@foobar:' follows a
section".

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <20230510141637.3685080-1-armbru@redhat.com>
Reviewed-by: Juan Quintela <quintela@redhat.com>
[Conflict with commit 3e32dca3f0 resolved]

scripts/qapi/parser.py

@@ -675,8 +675,8 @@ class QAPIDoc:
         match = self._match_at_name_colon(line)
         if match:
             raise QAPIParseError(self._parser,
-                                 "'@%s:' can't follow '%s' section"
-                                 % (match.group(1), self.sections[0].name))
+                                 "description of '@%s:' follows a section"
+                                 % match.group(1))
         match = self._match_section_tag(line)
         if match:
             line = line[match.end():]

tests/qapi-schema/doc-interleaved-section.err

@@ -1 +1 @@
-doc-interleaved-section.json:15:1: '@foobar:' can't follow 'Note' section
+doc-interleaved-section.json:15:1: description of '@foobar:' follows a section