Use entry-points-selectable compatibility shim.

Adds forward-compatibility for entry_points.
Fixes deprecation warnings.
See: python/importlib_metadata#298

pyproject.toml

@@ -27,7 +27,7 @@ module = [
     "nitrate.*",
     "pylero.*",
     "testcloud.*",
-    "importlib_metadata",
+    "backports.entry_points_selectable",
     "mrack.*",
 ]
 ignore_missing_imports = true

setup.py

@@ -56,6 +56,7 @@
     'ruamel.yaml',
     'jinja2',
     'setuptools',
+    'backports.entry_points_selectable',  # Required for importlib_metadata < 3.6 (Python < 3.10)
     ]
 
 # typing_extensions is needed with Python 3.7 and older, types imported
@@ -66,9 +67,6 @@
 # dataclasses is needed with Python 3.6
 install_requires.append("dataclasses; python_version < '3.7'")
 
-# entry_points is part of Python 3.9+
-install_requires.append("importlib_metadata; python_version < '3.9'")
-
 extras_require = {
     'docs': [
         'sphinx>=3',

tmt/plugins/__init__.py

@@ -8,10 +8,7 @@
 import sys
 from typing import Any, Generator, List, Optional, Tuple
 
-if sys.version_info < (3, 9):
-    from importlib_metadata import entry_points
-else:
-    from importlib.metadata import entry_points
+from backports.entry_points_selectable import entry_points
 
 import tmt
 from tmt.log import Logger
@@ -115,7 +112,7 @@ def _explore_entry_point(entry_point: str, logger: Logger) -> None:
     logger = logger.descend()
 
     try:
-        for found in entry_points()[entry_point]:
+        for found in entry_points(group=entry_point):
             logger.debug(f"Loading plugin '{found.name}' ({found.value}).")
             found.load()