"Sourness" has something of a negative connotation in terms of flavor of wine. However, in other contexts, such as "sweet and sour" chicken, sour candy, or a "whiskey sour" (drink), it's not a negative description. "Acidity" is a much more common description in writing about wine. "Tart" and "tartness" are also seen in many wine flavor descriptions.
The Wine Spectator has an article about acidity, tartness, and other aspects of wine flavor. Here is one interesting quote: "Hipster sommeliers and wine writers who consider themselves cutting edge favor tart, tangy wine styles."
Note that "acidity" has a scientific definition, involving pH (a measurement regime involving ions and electrons in chemistry), while tartness, sourness, and similar flavor terms do not (as far as I can determine).