azurestore: Work around error being not comparable

pkg/azurestore/azurestore.go

@@ -112,9 +112,13 @@ func (store AzureStore) GetUpload(ctx context.Context, id string) (handler.Uploa
 	}
 
 	offset, err := blockBlob.GetOffset(ctx)
-	if err != nil && err != handler.ErrNotFound {
+	if err != nil {
+		// Unpack the error and see if it is a handler.ErrNotFound by comparing the
+		// error code. If it matches, we ignore the error, otherwise we return the error.
+		if handlerErr, ok := err.(handler.Error); !ok || handlerErr.ErrorCode != handler.ErrNotFound.ErrorCode {
 			return nil, err
 		}
+	}
 
 	info.Offset = offset
 

pkg/handler/error.go

@@ -3,6 +3,8 @@ package handler
 // Error represents an error with the intent to be sent in the HTTP
 // response to the client. Therefore, it also contains a HTTPResponse,
 // next to an error code and error message.
+// TODO: Error is not comparable anymore because HTTPResponse
+// contains a map. See if we should change this.
 type Error struct {
 	ErrorCode    string
 	Message      string