qapi: Fix parse errors for removal of null from schema language

Commit 9d55380b5a "qapi: Remove null from schema language" (v4.2.0)
neglected to update two error messages.  Do that now.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <20210224101442.1837475-1-armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: John Snow <jsnow@redhat.com>

scripts/qapi/parser.py

@@ -236,9 +236,9 @@ def get_values(self):
         if self.tok == ']':
             self.accept()
             return expr
-        if self.tok not in "{['tfn":
+        if self.tok not in "{['tf":
             raise QAPIParseError(
-                self, "expected '{', '[', ']', string, boolean or 'null'")
+                self, "expected '{', '[', ']', string, or boolean")
         while True:
             expr.append(self.get_expr(True))
             if self.tok == ']':
@@ -257,12 +257,12 @@ def get_expr(self, nested):
         elif self.tok == '[':
             self.accept()
             expr = self.get_values()
-        elif self.tok in "'tfn":
+        elif self.tok in "'tf":
             expr = self.val
             self.accept()
         else:
             raise QAPIParseError(
-                self, "expected '{', '[', string, boolean or 'null'")
+                self, "expected '{', '[', string, or boolean")
         return expr
 
     def get_doc(self, info):

tests/qapi-schema/leading-comma-list.err

@@ -1 +1 @@
-leading-comma-list.json:2:13: expected '{', '[', ']', string, boolean or 'null'
+leading-comma-list.json:2:13: expected '{', '[', ']', string, or boolean

tests/qapi-schema/trailing-comma-list.err

@@ -1 +1 @@
-trailing-comma-list.json:2:36: expected '{', '[', string, boolean or 'null'
+trailing-comma-list.json:2:36: expected '{', '[', string, or boolean