Use StringIO instead of BytesIO in python3.

Status Job ID Name Coverage
  Build
failed #24085
build:2.7

failed #24086
build:3

 
  Test
skipped #24088
allowed to fail
lint:2.7
skipped #24092
allowed to fail
lint:3
skipped #24087
pyflakes:2.7
skipped #24091
pyflakes:3
skipped #24089
unittests:2.7
skipped #24093
unittests:3
skipped #24090
allowed to fail
unittests-modules:2.7
skipped #24094
allowed to fail
unittests-modules:3
 
  Deploy
skipped #24095
doc:2.7
skipped #24096
doc:3
 
Name Stage Failure
failed
build:3 Build There has been a timeout failure or the job got stuck. Check your timeout limits or try again
No job log
failed
build:2.7 Build There has been a timeout failure or the job got stuck. Check your timeout limits or try again
No job log