Lykke Li knows how to write a pop song. We all know this – every nightclub still religiously plays the Magician remix of ‘I Follow Rivers’. What the Swedish songwriter really knows though, is a sad pop song. Her latest release, so sad so sexy is no different. This follow-up to 2014’s I Never Learn, which saw her swing more toward the acoustic side of things, dips instead into R&B and hip hop spheres and feels like a matured throwback to her debut album, Youth Novels, released a decade ago now. However, while it’s an evolved departure musically, lyrically, it’s…