Re: [gentoo-user] Gobbledegook error message from emerge.

[John Covici]

On Fri, 11 Dec 2020 13:08:55 -0500,
Alan Mackenzie wrote:
>
> Hello, Gentoo.
>
> I'm angry, because I've wasted several hours trying to decypher a wholly
> unintuitive error "message" from emerge.  Because of this, it's been too
> long since I've been able to update.  Help, please!
>
> The command I typed in was
>
>     # time emerge -auND @world.
>
> I got back a horrendously long list of packages to merge (most of them
> re-merges), followed by:
>
> emerge: there are no ebuilds built with USE flags to satisfy "dev-python/pycparser[python_targets_python3_6(-)?,python_targets_python3_7(-)?,python_targets_python3_8(-)?,python_targets_python3_9(-)?,-python_single_target_python3_6(-),-python_single_target_python3_7(-),-python_single_target_python3_8(-),-python_single_target_python3_9(-)]".
> !!! One of the following packages is required to complete your request:
> - dev-python/pycparser-2.20-r1::gentoo (Change USE: +python_targets_python3_7)
> - dev-python/cffi-1.14.0-r3::gentoo (Change USE: -python_targets_python3_7)
> (dependency required by "dev-python/cffi-1.14.0-r3::gentoo" [ebuild])
> (dependency required by "dev-python/bcrypt-3.2.0::gentoo" [installed])
> (dependency required by "dev-python/paramiko-2.7.1::gentoo" [installed])
> (dependency required by "dev-vcs/bzr-2.7.0::gentoo" [installed])
> (dependency required by "@selected" [set])
> (dependency required by "@world" [argument])
>
> .  What is the syntax and semantics of that first line?  Is it explained
> somewhere in the emerge manual?  What do the square brackets mean?  What
> do the commas within these square brackes mean?  AND?  OR?  What about
> the question marks following minus signs inside parentheses?
>
> What does "(Change USE: +python_targets_python3_7)" mean?  Is it a
> suggestion to me that I should change some USE flag somewhere?  Or is it
> telling me that a changed USE flag is the reason for all the trouble?  Or
> does it mean something else?
>
> What is "dependency required by" supposed to mean?  I can understand a
> dependency of A on B.  I can understand A being required by B.  But a
> dependency being required?  what does this mean?
>
> Presumably to get out of the mess I've got to do something with one of
> the packages which "is required to complete your request".
>
> Surely somebody in the Gentoo portage team must see that printing human
> readable error messages is a worthwhile thing to do.  Surely?

Well, what portage is trying to tell you is that you need to change or
add a file  in your /etc/portage/package.use directory to specify
dev-python/pycparser python_targets_python3_7
and that should fix it  -- and if you have --autounmask-use =y (which
is the default) it should write the changes for you and after fixing
up your package.use file or directlry if necessary, you can proceed.

I hope that helps.

-- 
Your life is like a penny.  You're going to lose it.  The question is:
How do
you spend it?

         John Covici wb2una
         covici@××××××××××.com