Gentoo readlineのslot conflictでemergeが進まない

Gentooのpipを使おうとすると最新のPythonを要求され、最新のPythonをemergeしようとしたら、最新のgccをemergeしなければならない。と、なったのが先日の話。
gccをアップデートしたなら、

emerge -uDN @world

をやらねば、なんだったらカーネルもアップデートしないと、"gccのバージョン違うドライバだよ!"って言われたりするので、やりたいなぁ。なんて思います。(思わないか?)

んで、やると、readlineというツールでslot conflictが発生します。

!!! Multiple package instances within a single package slot have been pulled
!!! into the dependency graph, resulting in a slot conflict:

sys-libs/readline:0

  (sys-libs/readline-7.0_p3:0/7::gentoo, ebuild scheduled for merge) pulled in by
    >=sys-libs/readline-7.0:0= required by (app-shells/bash-4.4_p12:0/0::gentoo, ebuild scheduled for merge)
    ^^                  ^^^^^^                                                                                                                                                       

  (sys-libs/readline-6.3_p8-r3:0/0::gentoo, installed) pulled in by
    sys-libs/readline:0/0= required by (sys-apps/util-linux-2.30.2:0/0::gentoo, installed)
                     ^^^^^                                                                                                   
    >=sys-libs/readline-6.2_p5-r1:0/0=[abi_x86_64(-)] required by (sys-libs/slang-2.3.0:0/0::gentoo, installed)
                                 ^^^^^                                                                                                             
    >=sys-libs/readline-4.1:0/0= required by (net-misc/ntp-4.2.8_p10-r1:0/0::gentoo, installed)
                           ^^^^^                                                                                                   
    >=sys-libs/readline-4.1:0/0= required by (dev-lang/python-2.7.14-r1:2.7/2.7::gentoo, installed)
                           ^^^^^                                                                                                       
    sys-libs/readline:0/0= required by (sci-libs/libqalculate-0.9.9:0/6::gentoo, installed)
                     ^^^^^                                                                                                     
    >=sys-libs/readline-4.1:0/0= required by (dev-lang/python-3.6.3-r1:3.6/3.6m::gentoo, installed)
                           ^^^^^                                                                                                       
    sys-libs/readline:0/0= required by (dev-libs/libpcre-8.41-r1:3/3::gentoo, installed)
                     ^^^^^                                                                                                 
    >=sys-libs/readline-6.2_p5-r1:0/0=[abi_x86_64(-)] required by (dev-db/unixODBC-2.3.4-r1:0/0::gentoo, installed)
                                 ^^^^^                                                                                                                 
    sys-libs/readline:0/0=[abi_x86_64(-)] required by (dev-db/sqlite-3.20.1-r1:3/3::gentoo, installed)
                     ^^^^^                                                                                                               
    sys-libs/readline:0/0= required by (net-wireless/bluez-5.47-r1:0/3::gentoo, installed)
                     ^^^^^                                                                                                   
lang/python-3.5.4-r1:3.5/3.5m::gentoo, installed)
                           ^^^^^                                                                                                       
    >=sys-libs/readline-5.2:0/0= required by (sys-block/parted-3.2-r1:0/0::gentoo, installed)
                           ^^^^^                                                                                                 
    sys-libs/readline:0/0= required by (app-text/hunspell-1.6.1-r1:0/1.6::gentoo, installed)
                     ^^^^^                                                                                                     
    sys-libs/readline:0/0= required by (dev-lang/ruby-2.2.9:2.2/2.2::gentoo, installed)
                     ^^^^^                                                                                                 
    sys-libs/readline:0/0= required by (app-crypt/gnupg-2.2.0:0/0::gentoo, installed)
                     ^^^^^                                                                                               

It may be possible to solve this problem by using package.mask to
prevent one of those packages from being selected. However, it is also
possible that conflicting dependencies exist such that they are
impossible to satisfy simultaneously.  If such a conflict exists in
the dependencies of two different packages, then those packages can
not be installed simultaneously.

For more information, see MASKED PACKAGES section in the emerge man
page or refer to the Gentoo Handbook.

すみません。いくつかのパッケージ端折ってます。
これ、どうにかするには、

/etc/portage/package.use

に、

dev-lang/python sqlite

という1行を追加して、pythonのUSEフラグに"sqlite"を追加し、

emerge dev-lang/python

で、pythonをemergeし直してから、@worldをemergeすると、slot conflict問題は解決するそうです。

出典
Gentoo Forums :: View topic - [SOLVED] sys-libs/readline slot slot conflict