c.InteractiveShellApp.pylab not working

Like the title says setting c.InteractiveShellApp.pylab in profile_default/ipython_config.py does not have any effect. Settings on c.InteractiveShellApp.matplotlib work on the other hand.

To reproduce set `c.InteractiveShellApp.pylab =` something other than your default backend. It will always start with the default backend. I've tried to chase this down, but only found that the backend keyword remains at `'auto'`, even when setting the variable to something else. I've tried to compare where this differs from `c.interactiveShellApp.matplotlib` which works, but could not find where those to diverge. I see this both in 7.5 and 7.7.