(forward from rhbz#1684043)

Description of problem:
When I do rebuild from package details [1], I am not redirected to any sane place. Instead, page with empty script shows.

How reproducible:
always

Steps to Reproduce:
1. Visit package details, switch to custom method.
2. Push button
3.

Actual results:
Script edit box is empty, like I lost my script modifications [2]

Expected results:
Like SCM, i should be redirected to package builds instead [3]

1. https://COPR_HOST/coprs/USER/PROJECT/package/PACKAGE/rebuild
2. https://COPR_HOST/coprs/USER/PROJECT/add_build_custom/
3. https://COPR_HOST/coprs/USER/PACKAGE/builds/