Description of problem:
When trying to use custom certificates capsule-certs-generate returns below error

Traceback (most recent call last):
15: from /usr/sbin/capsule-certs-generate:58:in `<main>'
14: from /usr/share/gems/gems/kafo-7.3.0/lib/kafo/kafo_configure.rb:54:in `run'
13: from /usr/share/gems/gems/clamp-1.3.2/lib/clamp/command.rb:140:in `run'
12: from /usr/share/gems/gems/kafo-7.3.0/lib/kafo/kafo_configure.rb:184:in `run'
11: from /usr/share/gems/gems/clamp-1.3.2/lib/clamp/command.rb:66:in `run'
10: from /usr/share/gems/gems/kafo-7.3.0/lib/kafo/kafo_configure.rb:214:in `execute'
9: from /usr/share/gems/gems/kafo-7.3.0/lib/kafo/hooking.rb:65:in `execute'
8: from /usr/share/gems/gems/kafo-7.3.0/lib/kafo/hooking.rb:65:in `each'
7: from /usr/share/gems/gems/kafo-7.3.0/lib/kafo/hooking.rb:67:in `block in execute'
6: from /usr/share/gems/gems/kafo-7.3.0/lib/kafo/hook_context.rb:19:in `execute'
5: from /usr/share/gems/gems/kafo-7.3.0/lib/kafo/hook_context.rb:19:in `instance_eval'
4: from /usr/sbin/capsule-certs-generate:45:in `block in <main>'
3: from /usr/share/ruby/open3.rb:390:in `capture2e'
2: from /usr/share/ruby/open3.rb:208:in `popen2e'
1: from /usr/share/ruby/open3.rb:213:in `popen_run'
/usr/share/ruby/open3.rb:213:in `spawn': wrong first argument (ArgumentError)

Version-Release number of selected component (if applicable):
6.15.0.2.1

How reproducible:
Always

Steps to Reproduce:
1. Create custom ssl certificates
2. katello-certs-check -t capsule -k capsule.key -c capsule.pem -b CA.pem
...

Validation succeeded

To use them inside a NEW $CAPSULE, run this command:

capsule-certs-generate --foreman-proxy-fqdn "$CAPSULE" \
--certs-tar "~/$CAPSULE-certs.tar" \
--server-cert "/root/ssl/cap/capsule.pem" \
--server-key "/root/ssl/cap/capsule.key" \
--server-ca-cert "/root/ssl/cap/CA.pem"

To use them inside an EXISTING $CAPSULE, run this command INSTEAD:

capsule-certs-generate --foreman-proxy-fqdn "$CAPSULE" \
--certs-tar "~/$CAPSULE-certs.tar" \
--server-cert "/root/ssl/cap/capsule.pem" \
--server-key "/root/ssl/cap/capsule.key" \
--server-ca-cert "/root/ssl/cap/CA.pem" \
--certs-update-server

3. run below

1. CAPSULE=capsule.example.com
2. capsule-certs-generate --foreman-proxy-fqdn "$CAPSULE" \
   --certs-tar "~/$CAPSULE-certs.tar" \
   --server-cert "/root/ssl/cap/capsule.pem" \
   --server-key "/root/ssl/cap/capsule.key" \
   --server-ca-cert "/root/ssl/cap/CA.pem"

Actual results:

Traceback (most recent call last):
15: from /usr/sbin/capsule-certs-generate:58:in `<main>'
14: from /usr/share/gems/gems/kafo-7.3.0/lib/kafo/kafo_configure.rb:54:in `run'
13: from /usr/share/gems/gems/clamp-1.3.2/lib/clamp/command.rb:140:in `run'
12: from /usr/share/gems/gems/kafo-7.3.0/lib/kafo/kafo_configure.rb:184:in `run'
11: from /usr/share/gems/gems/clamp-1.3.2/lib/clamp/command.rb:66:in `run'
10: from /usr/share/gems/gems/kafo-7.3.0/lib/kafo/kafo_configure.rb:214:in `execute'
9: from /usr/share/gems/gems/kafo-7.3.0/lib/kafo/hooking.rb:65:in `execute'
8: from /usr/share/gems/gems/kafo-7.3.0/lib/kafo/hooking.rb:65:in `each'
7: from /usr/share/gems/gems/kafo-7.3.0/lib/kafo/hooking.rb:67:in `block in execute'
6: from /usr/share/gems/gems/kafo-7.3.0/lib/kafo/hook_context.rb:19:in `execute'
5: from /usr/share/gems/gems/kafo-7.3.0/lib/kafo/hook_context.rb:19:in `instance_eval'
4: from /usr/sbin/capsule-certs-generate:45:in `block in <main>'
3: from /usr/share/ruby/open3.rb:390:in `capture2e'
2: from /usr/share/ruby/open3.rb:208:in `popen2e'
1: from /usr/share/ruby/open3.rb:213:in `popen_run'
/usr/share/ruby/open3.rb:213:in `spawn': wrong first argument (ArgumentError)

Expected results:
...
Preparing installation Done
Success!

To finish the installation, follow these steps:

Additional info:
If needed i can provide reproducer