Fix scope issue

Increase livetime of the the compressor instances
to the livetime of RootImportOCI. They create temporary
files which are referenced later and need to live longer
than the block they got created in

kiwi/system/root_import/oci.py

@@ -40,6 +40,7 @@ class RootImportOCI(RootImportBase):
     """
     def post_init(self, custom_args: Dict[str, str]):
         self.archive_transport = custom_args['archive_transport']
+        self.compressed_image_files: List[Compress] = []
 
     def sync_data(self):
         """
@@ -90,6 +91,11 @@ def _get_image_urls(self) -> List[str]:
             image_urls: List[str] = []
             for image_file in self.image_files:
                 compressor = Compress(image_file)
+                # Increase livetime of the the compressor instances
+                # to the livetime of RootImportOCI. They create
+                # temporary files which are referenced later and
+                # need to live longer than this loop block
+                self.compressed_image_files.append(compressor)
                 if compressor.get_format():
                     compressor.uncompress(True)
                     uncompressed_image = compressor.uncompressed_filename