Ansible yum module does not see repositories with option installroot - ansible

Question

I would like to install the base CentOS to a specify directory, example to /var/centos. The directory is empty. I usage the next command in yum:
yum --disablerepo='*' --enablerepo='base,updates' --releasever=7 --installroot=/var/centos groupinstall #core
This command installs the base system without any problems. I want to do the same through Ansible.
In Ansible I usage the next task:
- name: Install base CentOS
yum:
state: latest
name: "#core"
installroot: "/var/centos/"
disablerepo: "*"
enablerepo: "base,updates"
releasever: "7"
When executing a playbook I receive an error:
Cannot find a valid baseurl for repo: base/$releasever/x86_64
As I understand, the yum don't see any repo.
I make list:
- name: Install base CentOS
yum:
list: repos
installroot: "/var/centos/"
When I execute the task I receive nothing.
Why doesn't yum module see repos?
Updated.
Before performing the Install base task, I executed the command - rpm --root /var/centos --force --nodeps -ivh http://mirror.centos.org/centos/7/os/x86_64/Packages/centos-release-7-6.1810.2.el7.centos.x86_64.rpm, after that everything worked.
The final playbook:
vars:
root_path: "/var/centos/"
tasks:
- name: Install package centos-release-7-6.1810.2.el7.centos.x86_64.rpm
shell: rpm --root {{ root_path }} --force --nodeps -ivh http://mirror.centos.org/centos/7/os/x86_64/Packages/centos-release-7-6.1810.2.el7.centos.x86_64.rpm
- name: Install base CentOS
yum:
state: installed
name:
- "#core"
installroot: "{{ root_path }}"
disablerepo: "*"
enablerepo: "base,updates"
releasever: "7"