Fix not creating images when rebuild

cloud_build/cloud_build.py

@@ -508,7 +508,7 @@ Dir::Etc::preferencesparts "/var/empty";
         full_target = f'{target}.{kind}'
         tarball_name = f'{image}-{arch}.{kind}'
         tarball_path = self.out_dir / tarball_name
-        result = None
+        result: Optional[Path] = tarball_path
         apt_dir = self.work_dir / 'apt'
         with self.pushd(self.work_dir / 'mkimage-profiles'):
             if not self.should_rebuild(tarball_path):
@@ -527,8 +527,8 @@ Dir::Etc::preferencesparts "/var/empty";
 
                 if os.path.exists(tarball_path):
                     self.info(f'End building of {full_target} {arch}')
-                    result = tarball_path
                 else:
+                    result = None
                     self.build_failed(full_target, arch)
 
         return result

tests/test_rebuild.py

@@ -48,3 +48,18 @@ class TestErrors(TestCase):
             self.cb.create_images()
         except BuildError:
             self.fail(msg)
+
+    @mock.patch('subprocess.call', call.Call())
+    def test_dont_create_image_when_rebuild(self):
+        tarball = self.data_dir / 'out/docker_Sisyphus-x86_64.tar.xz'
+        tarball.touch()
+        self.cb.create_images()
+        image = (
+            self.data_dir
+            / 'images'
+            / 'Sisyphus'
+            / 'alt-sisyphus-rootfs-minimal-x86_64.tar.xz'
+        )
+        msg = 'Do not create image when rebuild'
+        if not image.exists():
+            self.fail(msg)