The Import Patrons tool does not load on MySQL 5.7 because of the default sql_mode: only_full_group_by.
This is the error I got: http://paste.koha-community.org/16
Can't use an undefined value as an ARRAY reference at /usr/lib/x86_64-linux-gnu/perl5/5.22/DBI.pm line 2083
If I change the sql_mode to a mysql 5.6 behavior the import page loads fine.
This should have been fixed by bug 21596.
*** This bug has been marked as a duplicate of bug 21596 ***