Only use backported importlib_metadata on Python < 3.8 (#4214)

Signed-off-by: Anders Kaseorg <andersk@mit.edu>

moto/core/models.py

@@ -11,12 +11,16 @@ from abc import abstractmethod
 from io import BytesIO
 from collections import defaultdict
 
+try:
+    from importlib.metadata import version
+except ImportError:
+    from importlib_metadata import version
+
 from botocore.config import Config
 from botocore.handlers import BUILTIN_HANDLERS
 from botocore.awsrequest import AWSResponse
 from distutils.version import LooseVersion
 from http.client import responses as http_responses
-from importlib_metadata import version
 from urllib.parse import urlparse
 from werkzeug.wrappers import Request
 

setup.py

@@ -39,7 +39,7 @@ install_requires = [
     "MarkupSafe!=2.0.0a1",  # This is a Jinja2 dependency, 2.0.0a1 currently seems broken
     "Jinja2>=2.10.1",
     "more-itertools",
-    "importlib_metadata"
+    "importlib_metadata ; python_version < '3.8'"
 ]
 
 _dep_PyYAML = "PyYAML>=5.1"