ReplApplication: get_object should use do() to run fillobj

If backend.fillobj is called directly, all module errors will be raised
naked. They should be wrapped in BCallErrors so ReplApplication catches
them as usual.
This prevents a lot of application to crash when fillobj fails.
Status Job ID Name Coverage
  Build
failed #7998
build:2.7

failed #7999
build:3

 
  Test
skipped #8001
allowed to fail
lint:2.7
skipped #8004
allowed to fail
lint:3
skipped #8000
pyflakes:2.7
skipped #8003
pyflakes:3
skipped #8002
unittests:2.7
skipped #8005
unittests:3
 
  Deploy
skipped #8006
doc:2.7
skipped #8007
doc:3
 
Name Stage Failure
failed
build:3 Build There is an unknown failure, please try again
No job log
failed
build:2.7 Build There is an unknown failure, please try again
No job log