CentOS 6.10 upgrade to CentOS 7.x
There is not an officially supported direct upgrade path from CentOS 6.x to 7.x so the process is to backup the CentOS 6.x server, followed by a new install of CentOS 7.x and then import the back up data from you old CentOS 6.x server.
Red Hat does provide support of a major version upgrade from RHEL 6 to 7, but only in some specific scenario's with some rather strict requirements. The same also holds also for CentOS 6 --> 7 upgrades
See the Migration PLanning Guide for the current requirements and details, but one requirement is that:
Your system includes only the following package groups:
- Minimal
- Base
- Web Server
- DHCP Server
- NFS File Server (@nfs-server)
- Print Server
- CIFS file server
Remove other package groups before upgrading and reinstall them when your upgrade is complete.
The debug output you show that you (still) have packages installed from unsupported packages groups and repositories that are not in-scope for the upgrade tool :
python34-3.4.10-1.el7.x86_64 (epel)
php-common-5.6.40-9.el7.remi.x86_64 (remi-php56)
In general: do a fresh install rather than a major version upgrade.
Also with the recent release of RHEL 8 I wait a bit for the release of CentOS 8 : https://wiki.centos.org/About/Building_8