emerge -pqv =net-misc/curl-7.21.7-r2

!!! The ebuild selected to satisfy "=net-misc/curl-7.21.7-r2" has unmet requirements.
- net-misc/curl-7.21.7-r2::gentoo USE="gnutls ipv6 kerberos ldap nss ssl -ares -idn -libssh2 -static-libs -test -threads"

  The following REQUIRED_USE flag constraints are unsatisfied:
    nss? ( !gnutls )

  The above constraints are a subset of the following complete expression:
    threads? ( !ares ) gnutls? ( ssl ) nss? ( ssl ) nss? ( !gnutls )


 * IMPORTANT: 3 news items need reading for repository 'gentoo'.
 * Use eselect news to read news items.