Change syntax of list comprehension to work on RHEL 6 (Python 2.6)
Fixed unittest module incompatibility with Python 2.6
Whitespaces
Simplify as per elyezer's idea (https://github.com/lhellebr/robottelo/commit/624ac43e5a4afba313d7363dfd8964f581459805#commitcomment-5810048)