Add missing space that C++11 needs for macro expansion.

This silences the warning about "invalid suffix on literal".
4 jobs for master in 3 minutes and 31 seconds (queued for 2 seconds)
Status Name Job ID Coverage
  Test
passed mirror #8951

00:00:32

passed python2 #8949

00:00:29

passed python3 #8950

00:00:30

 
  Deploy
passed create conda dev package #8952

00:02:59