update: ensure that exceptions during the update process are logged

If an exception occurred during the update then we were managing to save
the update record, but we did not include the exception traceback in the
log for the update. Catch the exception and log it which ensures it gets
captured in the update record and still gets printed as well.

Signed-off-by: Paul Eggleton <paul.eggleton@linux.intel.com>

layerindex/update.py

@@ -540,6 +540,10 @@ def main():
     except KeyboardInterrupt:
         logger.info('Update interrupted, exiting')
         sys.exit(254)
+    except Exception:
+        import traceback
+        logger.error(traceback.format_exc().rstrip())
+        sys.exit(1)
     finally:
         update.log = ''.join(listhandler.read())
         update.finished = datetime.now()