From b908ea4365e4db470b94f215c06acc6c9995d667 Mon Sep 17 00:00:00 2001
From: fis <jm.yuan@outlook.com>
Date: Thu, 21 May 2020 05:54:29 +0800
Subject: [PATCH] Py35.

---
 python-package/xgboost/core.py | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/python-package/xgboost/core.py b/python-package/xgboost/core.py
index d55e2c81250a..b6760ef8d1ec 100644
--- a/python-package/xgboost/core.py
+++ b/python-package/xgboost/core.py
@@ -270,7 +270,8 @@ def _convert_unknown_data(data, meta=None, meta_type=None):
     else:
         import warnings
         warnings.warn(
-            f'Unknown data type {type(data)}, coverting it to csr_matrix')
+            'Unknown data type: ' + str(type(data)) +
+            ', coverting it to csr_matrix')
         try:
             data = scipy.sparse.csr_matrix(data)
         except Exception: