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

Calculating dependencies ...

!!! Problem resolving dependencies for =net-libs/libwebsockets-4.5.8-r1
 done!
Dependency resolution took 0.83 s (backtrack: 0/20).


!!! The ebuild selected to satisfy "=net-libs/libwebsockets-4.5.8-r1" has unmet requirements.
- net-libs/libwebsockets-4.5.8-r1::gentoo USE="dbus ipv6 lejp smtp ssl threads -access-log -caps -cgi -client -extensions -generic-sessions -http-proxy -http2 -libev -libevent -libuv -mbedtls -peer-limits -server-status -socks5 -sqlite3 -zip"

  The following REQUIRED_USE flag constraints are unsatisfied:
    smtp? ( libuv )

  The above constraints are a subset of the following complete expression:
    access-log? ( http2 ) generic-sessions? ( smtp sqlite3 ) http-proxy? ( client ) mbedtls? ( ssl ) smtp? ( libuv ) socks5? ( client http-proxy ) at-most-one-of ( libev libevent )