Implement Complete::is_err()
Implement Complete::is_err()

mlalic/eventual,seanmonstar/eventual,posix4e/eventual,benaryorg/eventual,blaenk/eventual,mlalic/eventual,sisirkoppaka/eventual,tempbottle/eventual,benaryorg/eventual,sisirkoppaka/eventual,blaenk/eventual,carllerche/eventual,posix4e/eventual,tempbottle/eventual,seanmonstar/eventual,carllerche/eventual