fix(ls): catch error if there is no snapshot

backupbot.py

@@ -201,7 +201,18 @@ def list_files(snapshot, path):
     cmd.append(snapshot)
     if path:
         cmd.append(path)
-    output = restic.internal.command_executor.execute(cmd)
+    try:
+        restic.cat.config()
+        output = restic.internal.command_executor.execute(cmd)
+    except ResticFailedError as error:
+        if 'no snapshot found' in str(error):
+            err_msg = f'There is no snapshot {snapshot}'
+            if SERVICE:
+                err_msg += f'for the app {SERVICE}'
+            logging.error(err_msg)
+            exit(1)
+        else:
+            raise error 
     output = output.replace('}\n{', '}|{')
     results = list(map(json.loads, output.split('|')))
     return results