create more flexible fixtures

[evgeni]

          I don't know how far you want to take this, but I think you can even make the URL a parameter so it can be overridden

def yum_repository(product, organization, foremanapi, url='https://fixtures.pulpproject.org/rpm-no-comps/'):
    repo = foremanapi.create('repositories', {'name': str(uuid.uuid4()), 'product_id': product['id'], 'content_type': 'yum', 'url': url})

Originally posted by @ekohl in #43 (comment)