Always validate Backup before restoring (#5632)

* Validate Backup always before restoring

Since #5519 we check the encryption password early in restore case.
This has the side effect that we check the file existance early too.
However, in the non-encryption case, the file is not checked early.

This PR changes the behavior to always validate the backup file before
restoring, ensuring both encryption and non-encryption cases are
handled consistently.

In particular, the last case of test_restore_immediate_errors actually
validates that behavior. That test should actually have failed so far.
But it seems that because we validate the backup shortly after freeze
anyways, the exception still got raised early enough.

A simply `await asyncio.sleep(10)` right after the freeze makes the
test case fail. With this change, the test works consistently.

* Address pylint

* Fix backup_manager tests

* Drop warning message

tests/api/test_backups.py

@@ -16,7 +16,11 @@ from supervisor.backups.backup import Backup
 from supervisor.const import CoreState
 from supervisor.coresys import CoreSys
 from supervisor.docker.manager import DockerAPI
-from supervisor.exceptions import AddonsError, HomeAssistantBackupError
+from supervisor.exceptions import (
+    AddonsError,
+    BackupInvalidError,
+    HomeAssistantBackupError,
+)
 from supervisor.homeassistant.core import HomeAssistantCore
 from supervisor.homeassistant.module import HomeAssistant
 from supervisor.homeassistant.websocket import HomeAssistantWebSocket
@@ -466,6 +470,7 @@ async def test_restore_immediate_errors(
     assert "only a partial backup" in (await resp.json())["message"]
 
     with (
+        patch.object(Backup, "validate_backup"),
         patch.object(
             Backup,
             "supervisor_version",
@@ -488,7 +493,11 @@ async def test_restore_immediate_errors(
         patch.object(
             Backup, "all_locations", new={None: {"path": None, "protected": True}}
         ),
-        patch.object(Backup, "validate_password", return_value=False),
+        patch.object(
+            Backup,
+            "validate_backup",
+            side_effect=BackupInvalidError("Invalid password"),
+        ),
     ):
         resp = await api_client.post(
             f"/backups/{mock_partial_backup.slug}/restore/partial",
@@ -497,7 +506,10 @@ async def test_restore_immediate_errors(
     assert resp.status == 400
     assert "Invalid password" in (await resp.json())["message"]
 
-    with patch.object(Backup, "homeassistant", new=PropertyMock(return_value=None)):
+    with (
+        patch.object(Backup, "validate_backup"),
+        patch.object(Backup, "homeassistant", new=PropertyMock(return_value=None)),
+    ):
         resp = await api_client.post(
             f"/backups/{mock_partial_backup.slug}/restore/partial",
             json={"background": True, "homeassistant": True},
@@ -944,7 +956,7 @@ async def test_restore_backup_from_location(
     body = await resp.json()
     assert (
         body["message"]
-        == f"Cannot open backup at {backup_local_path.as_posix()}, file does not exist!"
+        == f"Cannot validate backup at {backup_local_path.as_posix()}, file does not exist!"
     )
 
     resp = await api_client.post(