Increase coroutine default stack size to 5 MB

10 jobs for master in 595 minutes and 11 seconds (queued for 1 second)
Status Job ID Name Coverage
  Test
passed #3428
amd64
job_clang_amd64

04:55:07

passed #3429
amd64
job_clang_amd64_nosh

04:24:36

passed #3425
amd64
job_clang_py2_amd64

05:00:04

passed #3430
amd64
job_gcc_amd64

03:47:51

passed #3431
amd64
job_gcc_amd64_nosh

03:15:56

passed #3424
amd64
job_gcc_py2_amd64

03:58:34

failed #3423
amd64
job_clang_amd64

failed #3427
amd64
job_clang_amd64_nosh

failed #3422
amd64
job_gcc_amd64

failed #3426
amd64
job_gcc_amd64_nosh