Add the ability to download diffoci for multiple platforms

The hash list provided on the Github releases page is now bundled in the
`reproduce-image.py` script, and the proper hashes are checked after
download.

dangerzone/errors.py

@@ -126,6 +126,10 @@ class ImageNotPresentException(Exception):
     pass
 
 
+class MultipleImagesFoundException(Exception):
+    pass
+
+
 class ImageInstallationException(Exception):
     pass
 

dangerzone/updater/__init__.py

@@ -1,3 +1,10 @@
 import logging
 
 log = logging.getLogger(__name__)
+
+from .signatures import (
+    DEFAULT_PUBKEY_LOCATION,
+    is_update_available,
+    upgrade_container_image,
+    verify_local_image,
+)

dangerzone/util.py

@@ -8,7 +8,7 @@ from pathlib import Path
 try:
     import platformdirs
 except ImportError:
-    import appdirs as platformdirs
+    import appdirs as platformdirs  # type: ignore[no-redef]
 
 
 def get_config_dir() -> Path: