Ain't no sunshine when she's gone - Tradução em português

I haven't understood very well this sentence.

What is the correct translate for this?

Ain't and no are two negations in the same sentence, and I don't know what ain't replace in this case.
And about "she's gone", what is 's of that contraction? Is or has?

If it would be "has", it would strange, because I guess ain't is in the present.
And if it would be "is", what is the translation of "she is gone"?

I hope someone help me.