remove dependency on /usr/bin/python3

[pgajdos]

remove dependency on /usr/bin/python3 using %python3_fix_shebang{,_path} macros, [bsc#1212476]

See
https://trello.com/c/RE0ZBjLe/162-remove-dependency-on-usr-bin-python3-from-factory-packages
https://build.opensuse.org/request/show/1183849

[meaksh]

Thanks for your contribution @pgajdos, and sorry for the delay on a review here!

Unfortunately, we need some adjustments here to avoid breaking the build for other OSes that are using this same spec file.

[meaksh]

We use this exact spec file for building different the "salt" package for different OSes, including old SLE15 versions and CentOS8/RES8, as you can see here:

https://build.opensuse.org/package/show/systemsmanagement:saltstack:products:testing/salt

This makes changes on this spec file a little bit tricky, as i.a. %python3_fix_shebang and some other macros are not available for all those OSes.

I would recommend to isolate your changes under the scope of %if %{suse_version} >= 1600, to prevent affecting the other OSes.

[mcepl]

I would much prefer some kind of shim, that would be more robust:

# Compat stub for python3_fix_shebang_path
%{?!python3_fix_shebang_path:%define python3_fix_shebang_path(+abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789_-=) \\\
    myargs="%{**}" \
    for f in ${myargs}; do \
        [ -f "$f" ] && sed -i -e "1s@#\\!.*python.*@#\\!$(realpath %__python3)@" $f \
    done
    }