Convert V2 to use the blob uploader interface

data/registry_model/blobuploader.py

@@ -64,6 +64,20 @@ def retrieve_blob_upload_manager(repository_ref, blob_upload_id, storage, settin
 
   return _BlobUploadManager(repository_ref, blob_upload, settings, storage)
 
+@contextmanager
+def complete_when_uploaded(blob_upload):
+  """ Wraps the given blob upload in a context manager that completes the upload when the context
+      closes.
+  """
+  try:
+    yield blob_upload
+  except Exception as ex:
+    logger.exception('Exception when uploading blob `%s`', blob_upload.blob_upload_id)
+    raise ex
+  finally:
+    # Cancel the upload if something went wrong or it was not commit to a blob.
+    if blob_upload.committed_blob is None:
+      blob_upload.cancel_upload()
 
 @contextmanager
 def upload_blob(repository_ref, storage, settings, extra_blob_stream_handlers=None):
@@ -120,7 +134,7 @@ class _BlobUploadManager(object):
 
     if start_offset > 0 and start_offset > self.blob_upload.byte_count:
       logger.error('start_offset provided greater than blob_upload.byte_count')
-      return None
+      raise BlobUploadException()
 
     # Ensure that we won't go over the allowed maximum size for blobs.
     max_blob_size = bitmath.parse_string_unsafe(self.settings.maximum_blob_size)