port code to be python 3 compatible and make mirror and config dir settable from environment

[bmanojlovic]

it should work in both python2 and python3 now if using containers you could get configuration from environment variables

[pyther]

Thanks! I need to spend a few minutes taking a closer look at (I've been swamped), but it looks great at first glance.

[bmanojlovic]

i have updated PR with few more changes; use modifyrepo to add updateinfo into repodata added simple Dockerfile for future use from docker container add logic that will use all cpu cores in createrepo - speeding up regeneration of metadata

[viniciusferrao]

Now with RHEL8 in the wild this patch is a must.

[steftux]

I have done the same code changes before seeing this pull request. I would appreciate the merge into master.

[viniciusferrao]

I think the lead developer has abandoned the code. Not blaming he anyway, but perhaps out of time or lost interest in the project.