Bump the minimum required python version to 3.10

Drop support of EoL python versions for running system tests. The
maintenance cost of supporting end of life ecosystem, especially Python
3.6 on EL8 and the related outdated packages (pytest, dnspython, ...),
has become unreasonable.

(cherry picked from commit ac8e2905b8)

bin/tests/system/conftest.py

@@ -19,6 +19,7 @@ import subprocess
 import tempfile
 import time
 from typing import Dict, List, Optional
+import sys
 
 import pytest
 
@@ -30,6 +31,8 @@ import isctest
 # Silence warnings caused by passing a pytest fixture to another fixture.
 # pylint: disable=redefined-outer-name
 
+if sys.version_info[1] < 10:
+    raise RuntimeError("Python 3.10 or newer is required to run system tests.")
 
 # ----------------------- Globals definition -----------------------------
 
@@ -409,12 +412,6 @@ def system_test_dir(request, env, system_test_name, expected_artifacts):
         assert all(res.outcome == "passed" for res in test_results.values())
         return "passed"
 
-    def unlink(path):
-        try:
-            path.unlink()  # missing_ok=True isn't available on Python 3.6
-        except FileNotFoundError:
-            pass
-
     def check_artifacts(source_dir, run_dir):
         def check_artifacts_recursive(dcmp):
             def artifact_expected(path, expected):
@@ -459,7 +456,7 @@ def system_test_dir(request, env, system_test_name, expected_artifacts):
     # Create a convenience symlink with a stable and predictable name
     module_name = SYMLINK_REPLACEMENT_RE.sub(r"\1", str(request.node.path))
     symlink_dst = system_test_root / module_name
-    unlink(symlink_dst)
+    symlink_dst.unlink(missing_ok=True)
     symlink_dst.symlink_to(os.path.relpath(testdir, start=system_test_root))
 
     isctest.log.init_module_logger(system_test_name, testdir)
@@ -508,7 +505,7 @@ def system_test_dir(request, env, system_test_name, expected_artifacts):
         isctest.log.deinit_module_logger()
         if not keep:
             shutil.rmtree(testdir)
-            unlink(symlink_dst)
+            symlink_dst.unlink(missing_ok=True)
 
 
 @pytest.fixture(scope="module")

configure.ac

@@ -240,7 +240,7 @@ AM_CONDITIONAL([HAVE_PERL], [test -n "$PERL"])
 #
 # Python is optional, it is used only by some of the system test scripts.
 #
-AM_PATH_PYTHON([3.6], [], [:])
+AM_PATH_PYTHON([3.10], [], [:])
 AM_CONDITIONAL([HAVE_PYTHON], [test "$PYTHON" != ":"])
 
 AC_PATH_PROGS([PYTEST], [pytest-3 py.test-3 pytest py.test pytest-pypy], [])