changed return type of manipulator

6 jobs for master in 7 minutes and 14 seconds (queued for 5 minutes and 27 seconds)
Status Job ID Name Coverage
  Test
failed #7839
debian:10 clang-7-libcpp-17

00:01:59

passed #7838
debian:10 gcc-8-noassert-17

00:02:32

passed #7841
debian:9 clang-3.8-14

00:02:04

passed #7840
debian:9 gcc-6-14

00:01:37

passed #7842
ubuntu:16.04 gcc-5-14

00:01:27

passed #7843
ubuntu:18.04 clang-6-17

00:02:32

 
Name Stage Failure
failed
debian:10 clang-7-libcpp-17 Test
             ^
2 errors generated.
make[3]: *** [dune/common/test/CMakeFiles/charconvtest.dir/build.make:63: dune/common/test/CMakeFiles/charconvtest.dir/charconvtest.cc.o] Error 1
make[2]: *** [CMakeFiles/Makefile2:1355: dune/common/test/CMakeFiles/charconvtest.dir/all] Error 2
make[1]: *** [CMakeFiles/Makefile2:1008: CMakeFiles/build_tests.dir/rule] Error 2
make: *** [Makefile:574: build_tests] Error 2
--- Failed to build dune-common-extensions ---
Terminating dunecontrol due to previous errors!
ERROR: Job failed: exit code 1