Build with newer Python interpreter

The code requires capture_output as an argument to subprocess which was
introduced in Python 3.7, thus we can no longer builds against Python 3.6
default on SLE 15 and openSUSE Leap 15 and have to build against a newer
version of Python available with 15.4 and later.

package/python-kiwi-keg.spec

@@ -22,8 +22,10 @@
 %else
 %bcond_with libalternatives
 %endif
+%define python python
+%{?sle15_python_module_pythons}
+
 
-%define         skip_python2 1
 Name:           python-kiwi-keg
 Version:        2.1.1
 Release:        0
@@ -34,29 +36,22 @@ Source:         keg-%{version}.tar.gz
 BuildRoot:      %{_tmppath}/%{name}-%{version}-build
 BuildRequires:  %{python_module Jinja2}
 BuildRequires:  %{python_module Sphinx}
-BuildRequires:  %{python_module base >= 3.6}
 BuildRequires:  %{python_module setuptools}
 BuildRequires:  fdupes
 BuildArch:      noarch
 Requires:       python-Jinja2
 Requires:       python-PyYAML
 Requires:       python-docopt
 Requires:       python-schema
-Requires:       python3-kiwi >= 9.21.21
-%if %python_version_nodots < 37
-Requires:       python-iso8601
-%endif
+Requires:       python311-kiwi >= 9.21.21
 %if %{with libalternatives}
 Requires:       alts
 BuildRequires:  alts
 %else
 Requires(post): update-alternatives
 Requires(postun):update-alternatives
 %endif
-%if "%{python_flavor}" == "python3" || "%{python_provides}" == "python3"
-Provides:       python3-kiwi-keg = %version
-Obsoletes:      python3-kiwi-keg < %version
-%endif
+Obsoletes:      python3-kiwi-keg <= %version
 
 %python_subpackages
 
@@ -67,7 +62,7 @@ KEG is an image composition tool for KIWI image descriptions
 Summary:        An OBS service: generate KIWI description using KEG
 Group:          Development/Tools/Building
 Requires:       git
-Requires:       python3-kiwi-keg = %version
+Requires:       python311-kiwi-keg = %version
 
 %description -n obs-service-compose_kiwi_description
 This is a source service for openSUSE Build Service.
@@ -80,7 +75,6 @@ auto-generation of change log files from commit history.
 %setup -q -n keg-%{version}
 
 %build
-# Build Python 3 version
 %python_build
 
 # Build man pages