Update from tipfy: removed NotImplementedError.
Update from tipfy: removed NotImplementedError.

cklein/wtforms,jmagnusson/wtforms,Xender/wtforms,Aaron1992/wtforms,subyraman/wtforms,hsum/wtforms,pawl/wtforms,pawl/wtforms,Aaron1992/wtforms,skytreader/wtforms,crast/wtforms,wtforms/wtforms