Don't show a traceback for a python version error

(Bitbake rev: 44c325306e55336b7b416fd88b39874012a3f603)

Signed-off-by: Chris Larson <chris_larson@mentor.com>
Signed-off-by: Richard Purdie <rpurdie@linux.intel.com>

bitbake/bin/bitbake

@@ -30,7 +30,10 @@ sys.path.insert(0, os.path.join(os.path.dirname(os.path.dirname(__file__)),
 import optparse
 import warnings
 from traceback import format_exception
-import bb
+try:
+    import bb
+except RuntimeError, exc:
+    sys.exit(str(exc))
 from bb import event
 import bb.msg
 from bb import cooker