Description of problem:
When there are no repositories enabled, leapp fails with:

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ERRORS
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2021-02-16 00:55:42.235256 [ERROR] Actor: scan_subscription_manager_info
Message: Unable to use yum successfully
Summary:
Details: Command ['yum', 'clean', 'all'] failed with exit code 1.
Stderr: There are no enabled repos.
Run "yum repolist all" to see the repos you have.
To enable Red Hat Subscription Management repositories:
subscription-manager repos --enable <repo>
To enable custom repositories:
yum-config-manager --enable <repo>

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END OF ERRORS
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Version-Release number of selected component (if applicable):
leapp-0.11.1-1.el7_9.noarch

How reproducible:
Everytime

Steps to Reproduce:
1. disable all repos
2. leapp preupgrade
3.

Actual results:
Message: Unable to use yum successfully
Summary:
Details: Command ['yum', 'clean', 'all'] failed with exit code 1.
Stderr: There are no enabled repos.
Run "yum repolist all" to see the repos you have.
To enable Red Hat Subscription Management repositories:
subscription-manager repos --enable <repo>
To enable custom repositories:
yum-config-manager --enable <repo>

Expected results:
Leapp could enable all repos to clear cache

1. yum clean all --enablerepo=*

Additional info: