Fix compilation error when xerus is used with boost type traits

8 jobs for development in 17 minutes and 37 seconds (queued for 2 seconds)
Status Job ID Name Coverage
  Build Gcc Nocheck
passed #5110
job_make_gcc_nocheck

00:01:30

 
  Test Gcc Nocheck
passed #5111
job_test_gcc_nocheck

00:00:19

 
  Code Coverage
passed #5112
job_code_coverage

00:05:17

76.984%
 
  Build Python2
passed #5113
job_build_python2

00:02:00

 
  Build Python3
passed #5114
job_build_python3

00:01:59

 
  Test Python2
passed #5115
job_test_python2

00:03:44

 
  Build Clang
passed #5116
job_make_clang

00:02:27

 
  Test Clang
passed #5117
job_test_clang

00:00:17