The problem with a question like this is that "Blues" is just a word, and when you use a word, it means whatever you want it to mean. In some fields, some words have very well-defined formal meanings, but the field of giving names to styles of music is generally vauge and informal.
One person might have the firm belief that if you take a loping slide guitar riff and change the lyrics from "Woke up this morning, got no reason to live" to "Woke up this morning, my heart was full of joy", then it ain't "the Blues" any more. That person is right, according to their own personal definition.
But listen to Howlin' Wolf's "Killing Floor". Although the words aren't jolly, the music is upbeat; approaching gospel. A record store would probably file it in the Blues section. More specifically, it is "Chicago Blues".
So if someone says "That's too upbeat, it's not the Blues", who's right and who's wrong? Nobody, because it's just a word.
At risk of riling blues snobs, the movie soundtrack of The Blues Brothers is full of upbeat, jolly dance songs -- and although you could argue that a lot of those are soul songs, you could also validly classify most of it as Chicago Blues.