$\large{P(x) = 5x^{2015} + x^2 + x + 1}$

Let $P(x)$ be a polynomial as defined above with the roots of $P(x)$ being $x_1, x_2, x_3, \ldots, x_{2015}$. Find the value of:

$\large{\left(\prod_{i=1}^{2015} (1+x_i)\right ) \left( \sum_{i=1}^{2015} \frac{1}{1-x_i} \right )}$