nova-manage: Print, not raise, exceptions

Raising an exception means it is not possible to return a status code.
Seeing as the 'nova-manage' application is an interactive one, it's
viable to fix this by printing the exception rather than raising.

Change-Id: Ifa3f80e4f7dccada439ffc9363e9f1504c8c2da1
Closes-bug: #1538227

nova/cmd/manage.py

@@ -1497,6 +1497,6 @@ def main():
         ret = fn(*fn_args, **fn_kwargs)
         rpc.cleanup()
         return(ret)
-    except Exception:
-        print(_("Command failed, please check log for more info"))
-        raise
+    except Exception as ex:
+        print(_("error: %s") % ex)
+        return(1)