some Latex code no longer works in 9.3 W10

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Hi

this code below display Latex ok in 9.2 W10 but KO in 9.3 W10:

var('z0,z1',domain=CC)
var('n,k,K',domain='integer')

def binNewtonLatex(chooseN,chooseK,k,n0,n1,sumEnd,sumStart,z_0,z_1):

    return r'\sum_{'+str(k)+'='+str(sumStart)+'}^{'+str(sumEnd)+'}'+r'{' + \
        str(chooseN) + r' \choose ' + str(chooseK) + \
    r'}'+str(z_0) + '^{'+str(n0)+'}'+str(z_1)+ '^{'+str(n1)+'}'

commentsL=[]
commentsL.append(
        LatexExpr(r"\text{we can check easily that Newton binomial formula is ok for n=0,n=1,n=2,n=3}\\") + \
        LatexExpr( r"(z0+z1)^0 \,=\,"+binNewtonLatex( 0,k,k,k,0-k,0,0,z0,z1) + r" = 1 \\") + \
        LatexExpr(       r"(z0+z1)^1 \,=\,"+binNewtonLatex( 1,k,k,k,k,1,0,z0,z1) +r"= z0+z1 \\") )

for c in commentsL :
    show(c)