ALUMBRONES Opens on Friday Directed by Bruce Donnelly In Spanish, with English subtitles 1 hour 15 minutes; not rated The Cuban artists featured in Bruce Donnelly’s documentary “Alumbrones” are used to making do. Scarcity — of materials, of electricity, even of food — has been a condition of their creative lives. If we had money, one painting student says, maybe we wouldn’t be as interested in art. Short and sweet and limited, “Alumbrones” — it means little bursts of light, as when the electricity flickers on briefly during blackouts — is itself less interested in art than in these artists. And for good reason. They’re charming, insightful about life and art, and seemingly free of self-pity, with memorable faces and voices. By the end of the movie, they all feel a bit like pals.