fix py2 to py3 issue when running fit_bnb_coefs
fix py2 to py3 issue when running fit_bnb_coefs

bmvdgeijn/WASP,bmvdgeijn/WASP,gmcvicker/WASP,gmcvicker/WASP,gmcvicker/WASP,bmvdgeijn/WASP,bmvdgeijn/WASP,gmcvicker/WASP