introduce llnl.util.compat to remove sys.version_info checks (#21720)

- also split typing.py into typing_extensions and add py2 shims

lib/spack/llnl/util/compat.py

@@ -0,0 +1,39 @@
+# Copyright 2013-2022 Lawrence Livermore National Security, LLC and other
+# Spack Project Developers. See the top-level COPYRIGHT file for details.
+#
+# SPDX-License-Identifier: (Apache-2.0 OR MIT)
+# isort: off
+
+import sys
+
+if sys.version_info < (3,):
+    from itertools import ifilter as filter
+    from itertools import imap as map
+    from itertools import izip as zip
+    from itertools import izip_longest as zip_longest  # novm
+    from urllib import urlencode as urlencode
+    from urllib import urlopen as urlopen
+else:
+    filter = filter
+    map = map
+    zip = zip
+    from itertools import zip_longest as zip_longest  # novm # noqa: F401
+    from urllib.parse import urlencode as urlencode   # novm # noqa: F401
+    from urllib.request import urlopen as urlopen     # novm # noqa: F401
+
+if sys.version_info >= (3, 3):
+    from collections.abc import Hashable as Hashable                # novm
+    from collections.abc import Iterable as Iterable                # novm
+    from collections.abc import Mapping as Mapping                  # novm
+    from collections.abc import MutableMapping as MutableMapping    # novm
+    from collections.abc import MutableSequence as MutableSequence  # novm
+    from collections.abc import MutableSet as MutableSet            # novm
+    from collections.abc import Sequence as Sequence                # novm
+else:
+    from collections import Hashable as Hashable                # noqa: F401
+    from collections import Iterable as Iterable                # noqa: F401
+    from collections import Mapping as Mapping                  # noqa: F401
+    from collections import MutableMapping as MutableMapping    # noqa: F401
+    from collections import MutableSequence as MutableSequence  # noqa: F401
+    from collections import MutableSet as MutableSet            # noqa: F401
+    from collections import Sequence as Sequence                # noqa: F401

lib/spack/llnl/util/filesystem.py

@@ -21,15 +21,11 @@
 import six
 
 from llnl.util import tty
+from llnl.util.compat import Sequence
 from llnl.util.lang import dedupe, memoized
 
 from spack.util.executable import Executable
 
-if sys.version_info >= (3, 3):
-    from collections.abc import Sequence  # novm
-else:
-    from collections import Sequence
-
 __all__ = [
     'FileFilter',
     'FileList',

lib/spack/llnl/util/lang.py

@@ -14,17 +14,7 @@
 
 from six import string_types
 
-if sys.version_info < (3, 0):
-    from itertools import izip_longest  # novm
-    zip_longest = izip_longest
-else:
-    from itertools import zip_longest  # novm
-
-if sys.version_info >= (3, 3):
-    from collections.abc import Hashable, MutableMapping  # novm
-else:
-    from collections import Hashable, MutableMapping
-
+from llnl.util.compat import Hashable, MutableMapping, zip_longest
 
 # Ignore emacs backups when listing modules
 ignore_modules = [r'^\.#', '~$']