feat(s3-backend): add error handling to object retrieving

src/jcloud_s3fuse/s3/backend.py

@@ -13,6 +13,7 @@
 # limitations under the License.
 
 import httpx
+from .exceptions import S3InternalServerError, S3ObjectNotFoundError, S3ObjectPermissionError
 from typing import AsyncGenerator, Optional
 from urllib.parse import urljoin
 
@@ -58,5 +59,12 @@ class S3Backend:
                     urljoin(self.url, object_path),
                     headers = headers
             ) as response:
+                if response.status_code == 404:
+                    raise S3ObjectNotFoundError('Object not found', object_path = object_path)
+                if response.status_code == 403:
+                    raise S3ObjectPermissionError('Object access forbidden', object_path = object_path)
+                if response.status_code // 100 == 5:
+                    raise S3InternalServerError('Internal server error')
+
                 async for chunk in response.aiter_bytes():
                     yield chunk