These are the packages that would be merged, in order:

Calculating dependencies ...

!!! Problem resolving dependencies for =net-dns/opendnssec-2.1.13-r2
 done!
Dependency resolution took 0.84 s (backtrack: 0/20).


!!! The ebuild selected to satisfy "=net-dns/opendnssec-2.1.13-r2" has unmet requirements.
- net-dns/opendnssec-2.1.13-r2::gentoo USE="mysql readline signer softhsm sqlite -debug -doc -external-hsm -opensc -test"

  The following REQUIRED_USE flag constraints are unsatisfied:
    exactly-one-of ( mysql sqlite )

  The above constraints are a subset of the following complete expression:
    exactly-one-of ( mysql sqlite ) exactly-one-of ( softhsm opensc external-hsm )