SSL certificate error

[John Emmas <john creativepost co uk>]

I haven't needed to access gnome/git repos for a while but I tried this 
morning and every repo gives me an error about an expired SSL 
certificate.  For example, here's what I see when trying to pull from 
gtkmm:-

     Fetching origin
     fatal: unable to access 'https://gitlab.gnome.org/GNOME/gtkmm/': 
SSL certificate problem: certificate has expired

I'm guessing I need to add / change something here?  But what..?

Thanks, John