fix the version comparison for importlib usage

This commit uses the python version 3.8 as
last version to use `importlib_metadata`.
The previous code tried to use
`importlib_metadata` on python 3.9, which
fails.

The commit also adapts the `entry_points()`
calls in  `get_extractor_class` to python 3.9,
where `entry_points` does not support
keyword-arguments

datalad_metalad/extract.py

@@ -490,7 +490,7 @@ def get_extractor_class(extractor_name: str) -> Union[
                                             Type[FileMetadataExtractor]]:
 
     """ Get an extractor from its name """
-    if sys.version_info < (3, 10):
+    if sys.version_info < (3, 9):
         from importlib_metadata import entry_points
     else:
         from importlib.metadata import entry_points
@@ -502,21 +502,21 @@ def get_extractor_class(extractor_name: str) -> Union[
     # from datalad core.
     entry_point_list = [
         entry_point
-        for entry_point in entry_points(
-            group="datalad.metadata.extractors",
-            name=extractor_name,
-        )
-        if entry_point.dist.name != "datalad"
+        for group, group_entries in entry_points().items()
+        for entry_point in group_entries
+        if group == "datalad.metadata.extractors"
+        and entry_point.name == extractor_name
+        and entry_point.dist.name != "datalad"
     ]
 
     if not entry_point_list:
         entry_point_list = [
             entry_point
-            for entry_point in entry_points(
-                group="datalad.metadata.extractors",
-                name=extractor_name,
-            )
-            if entry_point.dist.name == "datalad"
+            for group, group_entries in entry_points().items()
+            for entry_point in group_entries
+            if group == "datalad.metadata.extractors"
+            and entry_point.name == extractor_name
+            and entry_point.dist.name == "datalad"
         ]
 
     if not entry_point_list:

datalad_metalad/extractors/tests/test_base.py

@@ -11,7 +11,7 @@
 import sys
 
 import pytest
-if sys.version_info < (3, 10):
+if sys.version_info < (3, 9):
     from importlib_metadata import entry_points
 else:
     from importlib.metadata import entry_points

datalad_metalad/filter.py

@@ -286,7 +286,7 @@ def run_filter(filter_name: str,
 
 def get_filter_class(filter_name: str) -> Type[MetadataFilterBase]:
     """ Get a filter class from its name"""
-    if sys.version_info < (3, 10):
+    if sys.version_info < (3, 9):
         from importlib_metadata import entry_points
     else:
         from importlib.metadata import entry_points

datalad_metalad/utils.py

@@ -4,7 +4,7 @@
 from pathlib import Path
 from typing import Dict, List, Union
 
-if sys.version_info < (3, 10):
+if sys.version_info < (3, 9):
     from importlib_resources import files
 else:
     from importlib.resources import files

requirements.txt

@@ -1,6 +1,7 @@
 datalad>=0.18
-sphinx>=1.7.8
-sphinx-rtd-theme
+datalad-metadata-model>=0.3.10
+importlib-resources
 pytest
 pyyaml
-datalad-metadata-model>=0.3.10
+sphinx>=1.7.8
+sphinx-rtd-theme