Gasoline markets in Africa and nearby regions are tightening as the biggest refinery in Africa, the Dangote plant in Nigeria, has slashed crude oil purchases in recent weeks amid operational challenges. The refinery is set to buy fewer than 300,000 barrels per day (bpd) of crude oil in October, Bloomberg reported on Thursday, citing vessel-tracking data and allocation lists. That’s half compared to the over 600,000 bpd purchases in July. The gasoline unit at the plant has been a substantial supplier of the fuel in Nigeria…