dangerzone.updater exposes a few funtions, constants and exceptions

This is done to avoid looking at the internal logic of
`dangerzone.updater`. Only the features that actually are part of
the exposed API are exposed, and do not require deep knowledge of the
updater's logic to be used.

dangerzone/isolation_provider/container.py

@@ -3,11 +3,20 @@ import os
 import platform
 import shlex
 import subprocess
-from typing import Callable, List, Tuple
+import sys
+from typing import Callable, List, Optional, Tuple
 
-from .. import container_utils, errors, updater
-from ..container_utils import Runtime
+from .. import container_utils, errors
+from ..container_utils import CONTAINER_NAME, Runtime
 from ..document import Document
+from ..updater import (
+    DEFAULT_PUBKEY_LOCATION,
+    UpdaterError,
+    install_local_container_tar,
+    is_update_available,
+    upgrade_container_image,
+    verify_local_image,
+)
 from ..util import get_resource_path, get_subprocess_startupinfo
 from .base import IsolationProvider, terminate_process_group
 

dangerzone/updater/__init__.py

@@ -1,3 +1,12 @@
 import logging
 
 log = logging.getLogger(__name__)
+
+from .errors import SignatureError, UpdaterError
+from .signatures import (
+    DEFAULT_PUBKEY_LOCATION,
+    install_local_container_tar,
+    is_update_available,
+    upgrade_container_image,
+    verify_local_image,
+)