lookup_type() is capable of returning None, but some callers aren't
prepared for that and assume it will always succeed.

Use the must-not-fail variant resolve_type() instead, which guarantees
that the return type will not be None.

Signed-off-by: John Snow <jsnow@redhat.com>
---
 scripts/qapi/introspect.py | 4 ++--
 scripts/qapi/schema.py     | 3 +--
 2 files changed, 3 insertions(+), 4 deletions(-)

diff --git a/scripts/qapi/introspect.py b/scripts/qapi/introspect.py
index 67c7d89aae0..c38df61a6d5 100644
--- a/scripts/qapi/introspect.py
+++ b/scripts/qapi/introspect.py
@@ -227,10 +227,10 @@ def _use_type(self, typ: QAPISchemaType) -> str:
 
         # Map the various integer types to plain int
         if typ.json_type() == 'int':
-            typ = self._schema.lookup_type('int')
+            typ = self._schema.resolve_type('int')
         elif (isinstance(typ, QAPISchemaArrayType) and
               typ.element_type.json_type() == 'int'):
-            typ = self._schema.lookup_type('intList')
+            typ = self._schema.resolve_type('intList')
         # Add type to work queue if new
         if typ not in self._used_types:
             self._used_types.append(typ)
diff --git a/scripts/qapi/schema.py b/scripts/qapi/schema.py
index a77b51d1b96..35638c7708a 100644
--- a/scripts/qapi/schema.py
+++ b/scripts/qapi/schema.py
@@ -650,8 +650,7 @@ def check(self, schema, seen):
                     "discriminator '%s' is not a member of %s"
                     % (self._tag_name, base))
             # Here we do:
-            base_type = schema.lookup_type(self.tag_member.defined_in)
-            assert base_type
+            base_type = schema.resolve_type(self.tag_member.defined_in)
             if not base_type.is_implicit():
                 base = "base type '%s'" % self.tag_member.defined_in
             if not isinstance(self.tag_member.type, QAPISchemaEnumType):
-- 
2.43.0