bcrypt gem needs to be updated to work with libxcrypt.

Summary

Fedora 28 has switched from glibc libcrypt to libxcrypt. This breaks the bcrypt gem on versions before 3.1.12.

From GitLab-CE's Gemfile.lock bcrypt (3.1.11)

Attempting to install GitLab on Fedora 28 gives the error BCrypt::Errors::InvalidHash: invalid hash. Related issue

Steps to reproduce

Run gdk install on fedora 28. While running the migrations it will halt on this error

Possible fixes

A minor release of the bcrypt gem was released to fix this bug. Simply update the bcrypt gem from 3.1.11 to 3.1.12 to fix this bug.

Workaround

There is a hacky workaround for this issue by manually editing the gem code locally as described here.