Improved groupby error message (c.f. Issue #525).
Improved groupby error message (c.f. Issue #525).

lenstr/rethinkdb,mbroadst/rethinkdb,mcanthony/rethinkdb,marshall007/rethinkdb,sontek/rethinkdb,bpradipt/rethinkdb,yakovenkodenis/rethinkdb,KSanthanam/rethinkdb,AntouanK/rethinkdb,grandquista/rethinkdb,Wilbeibi/rethinkdb,4talesa/rethinkdb,grandquista/rethinkdb,ajose01/rethinkdb,jesseditson/rethinkdb,tempbottle/rethinkdb,niieani/rethinkdb,marshall007/rethinkdb,sebadiaz/rethinkdb,matthaywardwebdesign/rethinkdb,mbroadst/rethinkdb,RubenKelevra/rethinkdb,wujf/rethinkdb,catroot/rethinkdb,Qinusty/rethinkdb,robertjpayne/rethinkdb,Wilbeibi/rethinkdb,mbroadst/rethinkdb,elkingtonmcb/rethinkdb,tempbottle/rethinkdb,sontek/rethinkdb,urandu/rethinkdb,jmptrader/rethinkdb,KSanthanam/rethinkdb,lenstr/rethinkdb,losywee/rethinkdb,scripni/rethinkdb,eliangidoni/rethinkdb,victorbriz/rethinkdb,niieani/rethinkdb,wkennington/rethinkdb,rrampage/rethinkdb,grandquista/rethinkdb,ayumilong/rethinkdb,grandquista/rethinkdb,mcanthony/rethinkdb,dparnell/rethinkdb,mbroadst/rethinkdb,jesseditson/rethinkdb,bpradipt/rethinkdb,losywee/rethinkdb,sbusso/rethinkdb,scripni/rethinkdb,Qinusty/rethinkdb,KSanthanam/rethinkdb,bchavez/rethinkdb,gdi2290/rethinkdb,victorbriz/rethinkdb,Qinusty/rethinkdb,ajose01/rethinkdb,lenstr/rethinkdb,yaolinz/rethinkdb,catroot/rethinkdb,victorbriz/rethinkdb,grandquista/rethinkdb,robertjpayne/rethinkdb,lenstr/rethinkdb,greyhwndz/rethinkdb,lenstr/rethinkdb,sontek/rethinkdb,4talesa/rethinkdb,mquandalle/rethinkdb,ajose01/rethinkdb,catroot/rethinkdb,yaolinz/rethinkdb,wkennington/rethinkdb,scripni/rethinkdb,marshall007/rethinkdb,ajose01/rethinkdb,matthaywardwebdesign/rethinkdb,elkingtonmcb/rethinkdb,alash3al/rethinkdb,robertjpayne/rethinkdb,matthaywardwebdesign/rethinkdb,yakovenkodenis/rethinkdb,ayumilong/rethinkdb,sontek/rethinkdb,niieani/rethinkdb,gavioto/rethinkdb,catroot/rethinkdb,lenstr/rethinkdb,sebadiaz/rethinkdb,losywee/rethinkdb,bpradipt/rethinkdb,bpradipt/rethinkdb,gavioto/rethinkdb,urandu/rethinkdb,gdi2290/rethinkdb,jmptrader/rethinkdb,elkingtonmcb/rethinkdb,yaolinz/rethinkdb,scripni/rethinkdb,ajose01/rethinkdb,sebadiaz/rethinkdb,RubenKelevra/rethinkdb,lenstr/rethinkdb,gavioto/rethinkdb,grandquista/rethinkdb,robertjpayne/rethinkdb,yaolinz/rethinkdb,alash3al/rethinkdb,captainpete/rethinkdb,mcanthony/rethinkdb,spblightadv/rethinkdb,wojons/rethinkdb,wujf/rethinkdb,matthaywardwebdesign/rethinkdb,marshall007/rethinkdb,yaolinz/rethinkdb,niieani/rethinkdb,dparnell/rethinkdb,yakovenkodenis/rethinkdb,jmptrader/rethinkdb,wkennington/rethinkdb,greyhwndz/rethinkdb,wojons/rethinkdb,greyhwndz/rethinkdb,yakovenkodenis/rethinkdb,Wilbeibi/rethinkdb,jesseditson/rethinkdb,sebadiaz/rethinkdb,rrampage/rethinkdb,greyhwndz/rethinkdb,grandquista/rethinkdb,mquandalle/rethinkdb,4talesa/rethinkdb,mcanthony/rethinkdb,captainpete/rethinkdb,ayumilong/rethinkdb,AntouanK/rethinkdb,RubenKelevra/rethinkdb,wkennington/rethinkdb,marshall007/rethinkdb,wojons/rethinkdb,RubenKelevra/rethinkdb,AntouanK/rethinkdb,RubenKelevra/rethinkdb,niieani/rethinkdb,JackieXie168/rethinkdb,mbroadst/rethinkdb,pap/rethinkdb,marshall007/rethinkdb,mquandalle/rethinkdb,eliangidoni/rethinkdb,wkennington/rethinkdb,mbroadst/rethinkdb,KSanthanam/rethinkdb,losywee/rethinkdb,pap/rethinkdb,Qinusty/rethinkdb,losywee/rethinkdb,eliangidoni/rethinkdb,mcanthony/rethinkdb,AntouanK/rethinkdb,sbusso/rethinkdb,marshall007/rethinkdb,urandu/rethinkdb,bchavez/rethinkdb,gdi2290/rethinkdb,wujf/rethinkdb,RubenKelevra/rethinkdb,greyhwndz/rethinkdb,elkingtonmcb/rethinkdb,scripni/rethinkdb,tempbottle/rethinkdb,wojons/rethinkdb,losywee/rethinkdb,jmptrader/rethinkdb,mquandalle/rethinkdb,Qinusty/rethinkdb,captainpete/rethinkdb,urandu/rethinkdb,captainpete/rethinkdb,tempbottle/rethinkdb,gdi2290/rethinkdb,dparnell/rethinkdb,matthaywardwebdesign/rethinkdb,marshall007/rethinkdb,ajose01/rethinkdb,dparnell/rethinkdb,elkingtonmcb/rethinkdb,gavioto/rethinkdb,rrampage/rethinkdb,pap/rethinkdb,ayumilong/rethinkdb,Wilbeibi/rethinkdb,jesseditson/rethinkdb,alash3al/rethinkdb,dparnell/rethinkdb,ajose01/rethinkdb,JackieXie168/rethinkdb,urandu/rethinkdb,catroot/rethinkdb,sbusso/rethinkdb,AntouanK/rethinkdb,bchavez/rethinkdb,bpradipt/rethinkdb,bchavez/rethinkdb,JackieXie168/rethinkdb,mbroadst/rethinkdb,mquandalle/rethinkdb,wkennington/rethinkdb,spblightadv/rethinkdb,robertjpayne/rethinkdb,rrampage/rethinkdb,jmptrader/rethinkdb,wkennington/rethinkdb,greyhwndz/rethinkdb,yakovenkodenis/rethinkdb,mcanthony/rethinkdb,alash3al/rethinkdb,bpradipt/rethinkdb,Qinusty/rethinkdb,wkennington/rethinkdb,spblightadv/rethinkdb,jmptrader/rethinkdb,greyhwndz/rethinkdb,wojons/rethinkdb,dparnell/rethinkdb,wujf/rethinkdb,sbusso/rethinkdb,scripni/rethinkdb,RubenKelevra/rethinkdb,sontek/rethinkdb,wujf/rethinkdb,Qinusty/rethinkdb,KSanthanam/rethinkdb,greyhwndz/rethinkdb,eliangidoni/rethinkdb,matthaywardwebdesign/rethinkdb,4talesa/rethinkdb,yaolinz/rethinkdb,robertjpayne/rethinkdb,4talesa/rethinkdb,gavioto/rethinkdb,wojons/rethinkdb,grandquista/rethinkdb,bchavez/rethinkdb,jmptrader/rethinkdb,captainpete/rethinkdb,yaolinz/rethinkdb,AntouanK/rethinkdb,robertjpayne/rethinkdb,eliangidoni/rethinkdb,gavioto/rethinkdb,dparnell/rethinkdb,catroot/rethinkdb,eliangidoni/rethinkdb,alash3al/rethinkdb,bchavez/rethinkdb,alash3al/rethinkdb,niieani/rethinkdb,matthaywardwebdesign/rethinkdb,Wilbeibi/rethinkdb,sbusso/rethinkdb,AntouanK/rethinkdb,victorbriz/rethinkdb,yakovenkodenis/rethinkdb,yaolinz/rethinkdb,captainpete/rethinkdb,bchavez/rethinkdb,catroot/rethinkdb,tempbottle/rethinkdb,tempbottle/rethinkdb,JackieXie168/rethinkdb,4talesa/rethinkdb,gdi2290/rethinkdb,rrampage/rethinkdb,sbusso/rethinkdb,AntouanK/rethinkdb,pap/rethinkdb,alash3al/rethinkdb,sbusso/rethinkdb,spblightadv/rethinkdb,eliangidoni/rethinkdb,bchavez/rethinkdb,ayumilong/rethinkdb,captainpete/rethinkdb,scripni/rethinkdb,rrampage/rethinkdb,4talesa/rethinkdb,jesseditson/rethinkdb,lenstr/rethinkdb,yakovenkodenis/rethinkdb,JackieXie168/rethinkdb,losywee/rethinkdb,losywee/rethinkdb,grandquista/rethinkdb,wojons/rethinkdb,mcanthony/rethinkdb,mquandalle/rethinkdb,sebadiaz/rethinkdb,yakovenkodenis/rethinkdb,urandu/rethinkdb,victorbriz/rethinkdb,spblightadv/rethinkdb,Qinusty/rethinkdb,wujf/rethinkdb,sbusso/rethinkdb,bchavez/rethinkdb,urandu/rethinkdb,spblightadv/rethinkdb,victorbriz/rethinkdb,KSanthanam/rethinkdb,sontek/rethinkdb,ayumilong/rethinkdb,sontek/rethinkdb,JackieXie168/rethinkdb,matthaywardwebdesign/rethinkdb,ayumilong/rethinkdb,spblightadv/rethinkdb,pap/rethinkdb,JackieXie168/rethinkdb,ayumilong/rethinkdb,victorbriz/rethinkdb,sebadiaz/rethinkdb,bpradipt/rethinkdb,gdi2290/rethinkdb,4talesa/rethinkdb,pap/rethinkdb,pap/rethinkdb,KSanthanam/rethinkdb,robertjpayne/rethinkdb,jesseditson/rethinkdb,mcanthony/rethinkdb,sebadiaz/rethinkdb,wujf/rethinkdb,JackieXie168/rethinkdb,mbroadst/rethinkdb,mbroadst/rethinkdb,gavioto/rethinkdb,tempbottle/rethinkdb,mquandalle/rethinkdb,niieani/rethinkdb,wojons/rethinkdb,rrampage/rethinkdb,captainpete/rethinkdb,niieani/rethinkdb,eliangidoni/rethinkdb,JackieXie168/rethinkdb,dparnell/rethinkdb,jesseditson/rethinkdb,dparnell/rethinkdb,scripni/rethinkdb,Qinusty/rethinkdb,ajose01/rethinkdb,bpradipt/rethinkdb,rrampage/rethinkdb,elkingtonmcb/rethinkdb,RubenKelevra/rethinkdb,urandu/rethinkdb,Wilbeibi/rethinkdb,pap/rethinkdb,victorbriz/rethinkdb,Wilbeibi/rethinkdb,robertjpayne/rethinkdb,elkingtonmcb/rethinkdb,jesseditson/rethinkdb,Wilbeibi/rethinkdb,tempbottle/rethinkdb,gdi2290/rethinkdb,gavioto/rethinkdb,spblightadv/rethinkdb,mquandalle/rethinkdb,catroot/rethinkdb,KSanthanam/rethinkdb,eliangidoni/rethinkdb,bpradipt/rethinkdb,sebadiaz/rethinkdb,jmptrader/rethinkdb,sontek/rethinkdb,elkingtonmcb/rethinkdb,alash3al/rethinkdb