[OE-core] [PATCH v4] runqemu: exit gracefully with an error message if qemu system is not evaluated

[Jagadeesh Krishnanjanappa]

It solves below error:
-- snip --
return 'qemu-system-%s' % qbsys
UnboundLocalError: local variable 'qbsys' referenced before assignment
-- snip --

[YOCTO #12846]

Signed-off-by: Jagadeesh Krishnanjanappa <jkrishnanjanappa at mvista.com>
---
 scripts/runqemu | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/scripts/runqemu b/scripts/runqemu
index f52b9a8..409d17c 100755
--- a/scripts/runqemu
+++ b/scripts/runqemu
@@ -1118,6 +1118,11 @@ class BaseConfig(object):
             qbsys = 'riscv64'
         elif mach == 'qemuriscv32':
             qbsys = 'riscv32'
+        else:
+            logger.error("Unable to determine QEMU PC System emulator for %s machine." % mach)
+            logger.error("As %s is not among valid QEMU machines such as," % mach)
+            logger.error("qemux86-64, qemux86, qemuarm64, qemuarm, qemumips64, qemumips64el, qemumipsel, qemumips, qemuppc")
+            raise RunQemuError("Set qb_system_name with suitable QEMU PC System emulator in .*qemuboot.conf.")
 
         return 'qemu-system-%s' % qbsys
 
-- 
1.8.3.1