Python3 compatbility fixes
Python3 compatbility fixes

mikecroucher/GPy,beckdaniel/GPy,esiivola/GPYgradients,PredictiveScienceLab/GPy,buntyke/GPy,Dapid/GPy,jameshensman/GPy,Dapid/GPy,ysekky/GPy,ptonner/GPy,ptonner/GPy,SheffieldML/GPy,PredictiveScienceLab/GPy,AlexGrig/GPy,maaskola/GPy,mikecroucher/GPy,AlexGrig/GPy,maaskola/GPy,avehtari/GPy,dhhjx880713/GPy,jameshensman/GPy,maaskola/GPy,beckdaniel/GPy,esiivola/GPYgradients,ptonner/GPy,Dapid/GPy,esiivola/GPYgradients,mikecroucher/GPy,dhhjx880713/GPy,befelix/GPy,buntyke/GPy,esiivola/GPYgradients,jameshensman/GPy,dhhjx880713/GPy,ptonner/GPy,avehtari/GPy,Dapid/GPy,buntyke/GPy,beckdaniel/GPy,dhhjx880713/GPy,avehtari/GPy,beckdaniel/GPy,befelix/GPy,maaskola/GPy,jameshensman/GPy,mikecroucher/GPy,PredictiveScienceLab/GPy,AlexGrig/GPy,befelix/GPy,SheffieldML/GPy,AlexGrig/GPy,ysekky/GPy,avehtari/GPy,ysekky/GPy,ysekky/GPy,buntyke/GPy,PredictiveScienceLab/GPy,befelix/GPy,SheffieldML/GPy,SheffieldML/GPy