Migrate to flake8.

Fixes bug 1172444.

Change-Id: Ia063ec67de9e6061ce38b948c9eb60b5589c7bb4
Migrate to pbr.

Fixes bug 1179007.

Change-Id: I66b78ec4b5ba70a1bf1e375a5d1b7575a1879730
Rename requires files to standard names.

Fixes bug 1179008.

Change-Id: I6765bb82df1ae672790662a30ee3527450685036