Calling preupgrade-assistant API directly

(cherry picked from commit a56bf742ce75fd03ea9c0a72bcfb7aee01533127)

Related: rhbz#1059447
Revise how preupgrade issues are printed

(cherry picked from commit 33b00ca07cfe03d0b167aed94313e6145925b18c)

Related: rhbz#1059447
New version 0.7.10