Description of problem:
When creating a new product and adding a new yum repo but not adding any content to it sync to capsule fails with 

Error: RPM1004: Error retrieving metadata: NOT FOUND

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

[root@inf3 ~]# rpm -qa satellite
satellite-6.2.12-5.0.el7sat.noarch
[root@inf3 ~]# rpm -qa foreman
foreman-1.11.0.85-1.el7sat.noarch
[root@inf3 ~]# 

[root@inf3 ~]# rpm -qa pulp*
pulp-katello-1.0.2-1.el7sat.noarch
pulp-docker-plugins-2.0.3.1-1.el7sat.noarch
pulp-puppet-tools-2.8.7.1-1.el7sat.noarch
pulp-puppet-plugins-2.8.7.1-1.el7sat.noarch
pulp-client-1.0-1.noarch
pulp-rpm-plugins-2.8.7.16-1.el7sat.noarch
pulp-selinux-2.8.7.15-1.el7sat.noarch
pulp-server-2.8.7.15-1.el7sat.noarch
[root@inf3 ~]# 

-- should be latest 6.2.12

How reproducible:


Steps to Reproduce:
1. create a new product, add new yum repository but don't add content
2. publish content view and promote content view to LCE 
3. add new LCE to capsule
4. sync capsule via hammer

Actual results:
# hammer capsule content synchronize --id 6 --organization-id 12
[.........................................................................................................................................................................................................] [100%]
Error: RPM1004: Error retrieving metadata: NOT FOUND

Expected results:
sync shall complete without error even if repository is empty 

Additional info:
Played around with fore metadata creation during publish and promote:
- when forcing metadata creation during publish only --> not sufficent, capsule sync fails
- when forcing metadata creation during promote only --> repo can be synced --> capsule sync works