Fixes MIP-692, MIP-719, MIP-737
Created by: mollyk
Fixes MIP-692, MIP-719, MIP-737 which comprise of small syntax changes, change a ValueError to a BadUserInput and fixing some warnings by changing Series.append to pd.concat.
Created by: mollyk
Fixes MIP-692, MIP-719, MIP-737 which comprise of small syntax changes, change a ValueError to a BadUserInput and fixing some warnings by changing Series.append to pd.concat.