### construction of extension field over GF(2^3)

My base field is GF(2^3) and to construct the field i am using irreducible polynomial p(x)=x^3+x+1. the extension field is GF(2^3)^2 and i want to construct this field using irreducible polynomial p(z)= z^2+(a^2+a+1)*z+a^2 where (a^2+a+1 and a^2 are the elements of field GF(2^3)) where a is represent theta that is root of irreducible polynomial over GF(2^3) .
i have written the code in sage but it gives me error .

K.=GF(2^3);K.modulus()
for i in enumerate(K): print i
K1.** = GF(K,'modulus=x^2+(a^2+a+1)*x+a^2');K1.modulus() **

** **