Poc/apiimport2.0

I would draw your attention on this method which is duplicate with VariantGroupHelper
https://github.com/akeneo/MagentoConnectorBundle/compare/2.0...poc/apiimport2.0?expand=1#diff-6a49e8e7b32d7ee80a0267bf717b57f5R116
https://github.com/akeneo/MagentoConnectorBundle/blob/poc/apiimport2.0/Normalizer/VariantGroupHelper.php#L108

Those class share nothing else than this method, is it possible to create an abstract or something ?
Cut this method en 2 protected methods:
 - one that check completeness
 - one that check belonging to channel
=> that would make your code easier to read