On a system with:

Linux 4.9.0-6-amd64
Debian 4.9.82-1+deb9u3 (2018-03-02) x86_64 (Stretch 9.4)
PHP 7.0.27-0+deb9u1
MySQL-MariaDB 5.5.5-10.1.26-MariaDB-0+deb9u1

executing the webinstaller located at /cgi-bin/koha/installer/install.pl I get this...


Web installer › Default data loaded
(...)
Optional data added
(...)

sample_patrons.sql

[Mon Mar 26 15:00:09 2018] install.pl: DBD::mysql::st execute failed: Cannot add or update a child row: a foreign key constraint fails (`koha_personal`.`borrowers`, CONSTRAINT `borrowers_ibfk_2` FOREIGN KEY (`branchcode`) REFERENCES `branches` (`branchcode`)) at /usr/share/perl5/DBIx/RunSQL.pm line 273.

(...)