Stack trace is being printed when runqemu fails, and it shouldn't. Here are two cases I found:

1) Built core-image-minimal for qemux86, then issued "runqemu qemuarm"

[humberto@localhost build]$ runqemu qemuarm
runqemu - INFO - Assuming MACHINE = qemuarm
runqemu - INFO - Running MACHINE=qemuarm bitbake -e...
runqemu - ERROR - /home/humberto/poky/build/tmp/deploy/images/qemuarm not a directory valid DEPLOY_DIR_IMAGE
runqemu - INFO - Running ls -t /home/humberto/poky/build/tmp/deploy/images/qemuarm/*.qemuboot.conf...
ls: cannot access '/home/humberto/poky/build/tmp/deploy/images/qemuarm/*.qemuboot.conf': No such file or directory
runqemu - INFO - Overriding conf file setting of STAGING_DIR_NATIVE to /home/humberto/poky/build/tmp/work/armv5e-poky-linux-gnueabi/defaultpkgname/1.0-r0/recipe-sysroot-native from Bitbake environment
Traceback (most recent call last):
  File "/home/humberto/poky/scripts/runqemu", line 1239, in <module>
    ret = main()
  File "/home/humberto/poky/scripts/runqemu", line 1226, in main
    config.check_and_set()
  File "/home/humberto/poky/scripts/runqemu", line 647, in check_and_set
    self.check_fstype()
  File "/home/humberto/poky/scripts/runqemu", line 508, in check_fstype
    raise Exception("FSTYPE is NULL!")
Exception: FSTYPE is NULL!

IMO, the issue is clear once the error is displayed, everything that comes after the ERROR is unneeded and not helpful. Maybe the error message could be improved, but either way I think the later part should be removed and leave it at:

[humberto@localhost build]$ runqemu qemuarm
runqemu - INFO - Assuming MACHINE = qemuarm
runqemu - INFO - Running MACHINE=qemuarm bitbake -e...
runqemu - ERROR - /home/humberto/poky/build/tmp/deploy/images/qemuarm not a directory valid DEPLOY_DIR_IMAGE


2) I run "runqemu qemux86 core-image-sato", which is wrong since I only built core-image-minimal. however the message is also sending a useless stack trace to the user:

[humberto@localhost build]$ runqemu qemux86 core-image-sato
runqemu - INFO - Assuming MACHINE = qemux86
runqemu - INFO - Running MACHINE=qemux86 bitbake -e...
runqemu - INFO - MACHINE: qemux86
runqemu - INFO - DEPLOY_DIR_IMAGE: /home/humberto/poky/build/tmp/deploy/images/qemux86
Traceback (most recent call last):
  File "/home/humberto/poky/scripts/runqemu", line 1239, in <module>
    ret = main()
  File "/home/humberto/poky/scripts/runqemu", line 1225, in main
    config.read_qemuboot()
  File "/home/humberto/poky/scripts/runqemu", line 692, in read_qemuboot
    raise Exception("Failed to find %s (wrong image name or BSP does not support running under qemu?)." % self.qemuboot)
Exception: Failed to find /home/humberto/poky/build/tmp/deploy/images/qemux86/core-image-sato-qemux86.qemuboot.conf (wrong image name or BSP does not support running under qemu?).

Could we just drop the stack trace and leave this at:

[humberto@localhost build]$ runqemu qemux86 core-image-sato
runqemu - INFO - Assuming MACHINE = qemux86
runqemu - INFO - Running MACHINE=qemux86 bitbake -e...
runqemu - INFO - MACHINE: qemux86
runqemu - INFO - DEPLOY_DIR_IMAGE: /home/humberto/poky/build/tmp/deploy/images/qemux86
Failed to find /home/humberto/poky/build/tmp/deploy/images/qemux86/core-image-sato-qemux86.qemuboot.conf (wrong image name or BSP does not support running under qemu?).


Both issues just require to show a simple, easy-to-understand message. Stack traces should be dropped and message clarity improved, if possible.