testrepository isn't maintained at this point but stestr is. Switch to stestr. Change-Id: I545cb1598cd232220aa4b61d0155ab5a2846fd29
Update boilerplate content, modernize for more recent PBR advancements, and get tests and style checks working. Change-Id: I86b6a171d2d81dd870f092542d2f4569a6772fac