Replaced check for sympy in constructors.py.
Replaced check for sympy in constructors.py.

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