Don't generate runtime dependency on setuptools for console_scripts entrypoints

- recent setuptools don't need it, they use importlib.metadata
- for this to work, we need to detect setuptools version
- the detection is not bulletproof, but it fallbacks to the old behavior

tests/console_script.sh

@@ -0,0 +1,71 @@
+#!/usr/bin/bash -eux
+RPMDIR=$(rpm --eval '%_topdir')/RPMS/noarch
+RPMPKG="${RPMDIR}/isort-5.7.0-0.noarch.rpm"
+
+mkdir -p $(rpm --eval '%_topdir')/SOURCES/
+
+spectool -g -R isort.spec
+
+for py_version in 3.6 3.7 3.8 3.9 3.10; do
+  rpmbuild -ba --define "python3_test_version ${py_version}" isort.spec
+
+  # sanity check for provides; if this is broken, so is the test
+  rpm -qp --provides ${RPMPKG} | grep "python${py_version}dist(isort)"
+
+  # only the "main" Python version has setuptools installed,
+  # everything else does not
+  if [ "$py_version" = "$(rpm --eval '%python3_version')" ]; then
+    # all main Python/setuptools versions in Fedora 33+ are recent enough
+    # not to justify a generated dependency wrt the console_script
+    rpm -qp --requires ${RPMPKG} | grep "python${py_version}dist(setuptools)" && exit 1 || true
+    rpm -qp --requires ${RPMPKG} | grep "python${py_version}dist(importlib-metadata)"  && exit 1 || true
+  else
+    # no setuptools installed, we assume an old version of setuptools was used to prepare the data
+    # hence the package always requires setuptools
+    rpm -qp --requires ${RPMPKG} | grep "python${py_version}dist(setuptools)"
+    rpm -qp --requires ${RPMPKG} | grep "python${py_version}dist(importlib-metadata)"  && exit 1 || true
+  fi
+
+  # the rest is only possible on the CI or in mock/container, where we are root
+  # never run this script as root on your host OS, it is destructive
+  # also, it only works once (improvements welcome)
+  test $EUID -ne 0 && continue
+  export RPM_BUILD_ROOT=/
+
+  # install setuptools and build again
+  python${py_version} -m ensurepip
+  rpmbuild -ba --define "python3_test_version ${py_version}" isort.spec
+
+  # the ensurepip version of setuptools is recent enough on Fedora 33+
+  # WARNING: Once we flip the rpmwheels bcond in python3.6, this assumption will break
+  rpm -qp --requires ${RPMPKG} | grep "python${py_version}dist(setuptools)"  && exit 1 || true
+  # but older Pythons still need importlib_metadata
+  if [[ "$py_version" = "3.6" || "$py_version" = "3.7" ]]; then
+    rpm -qp --requires ${RPMPKG} | grep "python${py_version}dist(importlib-metadata)"
+  else
+    rpm -qp --requires ${RPMPKG} | grep "python${py_version}dist(importlib-metadata)" && exit 1 || true
+  fi
+
+  # install setuptools 47.2 and build again
+  python${py_version} -m pip uninstall --yes setuptools
+  python${py_version} -m pip install 'setuptools>=47.2.0,<47.3.0'
+  rpmbuild -ba --define "python3_test_version ${py_version}" isort.spec
+
+  # this version of setuptools never uses importlib_metadata
+  rpm -qp --requires ${RPMPKG} | grep "python${py_version}dist(importlib-metadata)"  && exit 1 || true
+  # older Pythons use setuptools, newer Pythons use importlib.metadata
+  if [[ "$py_version" = "3.6" || "$py_version" = "3.7" ]]; then
+    rpm -qp --requires ${RPMPKG} | grep "python${py_version}dist(setuptools)"
+  else
+    rpm -qp --requires ${RPMPKG} | grep "python${py_version}dist(setuptools)" && exit 1 || true
+  fi
+
+  # install an even older setuptools version and build again
+  python${py_version} -m pip uninstall --yes setuptools
+  python${py_version} -m pip install 'setuptools<47.2.0'
+  rpmbuild -ba --define "python3_test_version ${py_version}" isort.spec
+
+  # old console_scripts entyrpoint used pkg_resources only
+  rpm -qp --requires ${RPMPKG} | grep "python${py_version}dist(setuptools)"
+  rpm -qp --requires ${RPMPKG} | grep "python${py_version}dist(importlib-metadata)"  && exit 1 || true
+done