all: Drop the need for install-time 2to3.

Preserve py2.7 compatibility.
Also, make pylint happier with the result.
2 jobs for master in 0 seconds
Status Job ID Name Coverage
  External
passed SlapOS.Eggs.UnitTest-Master.Python2

00:13:41

passed SlapOS.Eggs.UnitTest-Master.Python3

00:26:21