Cloned from https://bugzilla.redhat.com/show_bug.cgi?id=1807073

Description of problem:

Unable to render iPXE template 'Kickstart default iPXE': no implicit conversion of URI::HTTP into String"]

Version-Release number of selected component (if applicable):

How reproducible:

Steps to Reproduce:
1. Create a Host and fill all the mandatory fields
2. Under the 'Parameters' tab, add a host parameter as below:
-> Name: kickstart_liveimg
-> Type: string
-> Value: custom/RHEL_8_Image/RHEL_8_Image/devserver2-1.tar.xz

3. Click on 'Submit'

Actual results:
We get the below message:
---
The following errors may prevent a successful build:

Templates

Failure parsing Kickstart default iPXE: no implicit conversion of URI::HTTP into String.
---
Expected results:
The build finishes successfully

Additional info:
Workaround:
Change 'Kickstart default iPXE' template as below:

Modify the line below from:
stage2 = host_param('kickstart_liveimg') ? 'inst.stage2=' + medium_uri : ''
To:
stage2 = host_param('kickstart_liveimg') ? 'inst.stage2=' + medium_uri.to_s : ''