[plotters] replace cStringIO.StringIO with io.BytesIO to be python2 and python3 compatible

6 jobs for pil_show_image in 73 minutes and 25 seconds (queued for 31 minutes and 57 seconds)
Status Job ID Name Coverage
  Build
passed #136119
docker
build_linux_27

00:05:08

45.0%
passed #136120
docker
build_linux_36

00:20:19

45.0%
passed #136121
macosx
build_macosx_27

00:11:43

45.0%
passed #136122
macosx
build_macosx_36

00:11:10

45.0%
 
  Docker
passed #136123
docker-build
docker_linux_27

00:38:43

48.0%
passed #136124
docker-build
docker_linux_36

00:38:09

48.0%