Fix name.from_unicode to raise prorper exception
Fix name.from_unicode to raise prorper exception

Without this fix, UnicodeError exception was raised instead of
LabelTooLong

cluck/dnspython,leeclemens/dnspython,preo/dnspython,fjxhkj/dnspython,rcorrieri/dnspython,tow/dnspython,tomlanyon/dnspython,Abhayakara/dnspython