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

Calculating dependencies ...

!!! Problem resolving dependencies for =dev-ada/gnatcoll-db-25.0.0-r2
 done!
Dependency resolution took 0.84 s (backtrack: 0/20).


!!! The ebuild selected to satisfy "=dev-ada/gnatcoll-db-25.0.0-r2" has unmet requirements.
- dev-ada/gnatcoll-db-25.0.0-r2::gentoo USE="shared sql sqlite -db2ada -doc -gnatinspect -postgres -static-libs -static-pic -xref" ADA_TARGET="gcc_15 -gcc_12 -gcc_13 -gcc_14 (-gcc_16)" PYTHON_SINGLE_TARGET="-python3_12 -python3_13"

  The following REQUIRED_USE flag constraints are unsatisfied:
    exactly-one-of ( python_single_target_python3_12 python_single_target_python3_13 )

  The above constraints are a subset of the following complete expression:
    gnatinspect? ( xref ) xref? ( sqlite ) sqlite? ( sql ) db2ada? ( sql ) postgres? ( sql ) any-of ( shared static-libs static-pic ) any-of ( sql sqlite xref postgres gnatinspect db2ada ) exactly-one-of ( ada_target_gcc_13 ada_target_gcc_14 ada_target_gcc_15 ada_target_gcc_16 ) exactly-one-of ( python_single_target_python3_12 python_single_target_python3_13 )