Changing text for product add to cart error

I would like to change the default text of the message: “You already have this item in your cart” which happens when you have products that are sold individually. In class-wc-cart.php there is the following function:

if ( $product_data->is_sold_individually() ) {
	$in_cart_quantity = $cart_item_key ? $this->cart_contents[$cart_item_key]['quantity'] : 0;

	// If its greater than 0, its already in the cart
	if ( $in_cart_quantity > 0 ) {
		$woocommerce->add_error( sprintf('<a href="%s">%s</a> %s', get_permalink(woocommerce_get_page_id('cart')), __( 'View Cart →', 'woocommerce' ), __( 'You already have this item in your cart.', 'woocommerce' ) ) );
		return false;
	}
}

As you can see the text is defined above. How would I change this text using the functions.php file?

http://wordpress.org/extend/plugins/woocommerce/