Characters of SL_2(\mathbb{Z}/4\mathbb{Z})

Question

I need to have description of all the characters of group $\mathrm{SL}_2(\mathbb{Z}/8\mathbb{Z})$. I am implementing the following code on Sage online (changing the language to GAP).

\gap> g := SL(2, Integers mod 8);
gap> c := CharacterTable(g);
gap> Display(c);

But its giving me the many errors. How to fix this?