how to permanently USE-flag for one package

[falmer]

Hi forum,

 

recently I tried

emerge -aDNuv --with-bdeps=y @world

but got only

!!! The ebuild selected to satisfy "media-libs/lensfun" has unmet requirements.
- media-libs/lensfun-0.3.2::gentoo USE="-doc -test" CPU_FLAGS_X86="sse sse2" PYTHON_SINGLE_TARGET="python3_3 python3_4 -python3_5" PYTHON_TARGETS="python3_3 -python3_4 -python3_5"

  The following REQUIRED_USE flag constraints are unsatisfied:
    exactly-one-of ( python_single_target_python3_3 python_single_target_python3_4 python_single_target_python3_5 ) python_single_target_python3_4? ( python_targets_python3_4 )

So I do

PYTHON_SINGLE_TARGET="python3_3" emerge -av lensfun

that worked!

 

But if I try now

emerge -aDNuv --with-bdeps=y @world

it's the same problem.

 

How can I declare only for the lensfun package the PYTHON_SINGLE_TARGET permanently?

 

Merry xmas to all.

 

[cardinal]

Overriding_environment_variables_per_package

[j-g-]

You can also set this in /etc/portage/package.use, those environment variables are of a special kind that 'expands' into a use flag.
e.g.:
 

media-libs/lensfun python_single_target_python3_4

[falmer]

Thank you for the replies!

The way from cardinal worked well.

The way from j-g- doesn't, but it would be quite nice if the solution would be that easy.

[j-g-]

I just gave you the explanation of the flags, and hoped you would catch the working and solve it yourself, anyway look:
my gloabal variables for single target are python3.4, but lets try make lensfun use python3.5

I put this in /etc/portage/package.use:
 

media-libs/lensfun python_single_target_python3_5 -python_single_target_python3_4 python_targets_python3_5

And then:

$ sudo emerge -av lensfun

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

Calculating dependencies    ... done!                                 
[ebuild  N     ] media-libs/lensfun-0.3.2::gentoo  USE="-doc {-test}" CPU_FLAGS_X86="sse sse2" PYTHON_SINGLE_TARGET="python3_5 -python3_3 -python3_4" PYTHON_TARGETS="python3_4 python3_5 -python3_3" 767 KiB

Total: 1 package (1 new), Size of downloads: 767 KiB

Would you like to merge these packages? [Yes/No] n

Quitting.

It works, but I was hoping you could do this on your own.