add -s in user guide

3 jobs for master in 1 minute and 4 seconds
Status Name Job ID Coverage
  Py35
passed test-py3.5 #24082

00:00:23

91.0%
 
  Py36
passed test-py3.6 #24083

00:00:20

91.0%
 
  Py37
passed test-py3.7 #24084

00:00:20

91.0%