--- a/tests/tools/check_source.sh	Sat Jun 09 17:14:56 2018 +0300
+++ b/tests/tools/check_source.sh	Sat Jun 09 17:59:46 2018 +0300
@@ -322,7 +322,11 @@
             echo "Only changes will be checked"
             echo ""
             py_files=$(hg status -m -a -n -I '**.py')
-        fi
+            if [ -z "$py_files" ]; then
+                echo "No files to check"
+                exit 0;
+            fi
+       fi
     fi
 }