JOHANNESBURG—It is springtime dawn in Equestria, a far-eastern suburb of Pretoria, South Africa’s capital. A heatwave’s scalding the area, with a temperature well over 80F—even though it’s only 5.30 a.m. It is weather more characteristic of midsummer.  And things are about to get hotter.  A 20-strong group of men and women in plain clothes, some…