Failing to install mysql-server-5.6 on Wheezy 7

[Enchufadoo]

Hi, I'm trying for the first time Dotdeb repo on my workplace server running Debian 7, and I'm having trouble installing mysql-server-5.6

[ ok ] Stopping MySQL database server: mysqld.
2016-06-18 21:54:30 0 [Warning] TIMESTAMP with implicit DEFAULT value is deprecated. Please use --explicit_defaults_for_timestamp server option (see documentation for more details).
2016-06-18 21:54:30 0 [Note] /usr/sbin/mysqld (mysqld 5.6.29-1~dotdeb+7.1-log) starting as process 2027 ...
[....] Starting MySQL database server: mysqld-su: 44: [: -eq: unexpected operator
-su: 57: [[: not found
-su: 20: /etc/profile.d/extrapaths.sh: Bad substitution
invoke-rc.d: initscript mysql, action "start" failed.
dpkg: error processing mysql-server-5.6 (--configure):
 subprocess installed post-installation script returned error exit status 2
Errors were encountered while processing:
 mysql-server-5.6
E: Sub-process /usr/bin/dpkg returned an error code (1)

If I revert back to mysql-server-5.5 everything works great so far... even php 5.6 💃
But I wish I could fix that, seems the post install script is failing for some reason, I googled my eyes off but couldn't find anything related.

Any guidance is appreciated.