Fix remaining logic to support Python 3.6/7

... because this library no longer supports these old versions and
requires Python >= 3.8 now[1].

[1] 8efaa1ceb8

Change-Id: I2b229b24425d3afb9159b2479bd9547e3443011f

requirements.txt

@@ -3,4 +3,3 @@
 # process, which may cause wedges in the gate later.
 
 pbr!=2.1.0,>=2.0.0 # Apache-2.0
-importlib_metadata>=1.7.0;python_version<'3.8' # Apache-2.0

stevedore/_cache.py

@@ -15,6 +15,7 @@
 import errno
 import glob
 import hashlib
+import importlib.metadata as importlib_metadata
 import itertools
 import json
 import logging
@@ -23,13 +24,6 @@ import os.path
 import struct
 import sys
 
-try:
-    # For python 3.8 and later
-    import importlib.metadata as importlib_metadata
-except ImportError:
-    # For everyone else
-    import importlib_metadata
-
 
 log = logging.getLogger('stevedore._cache')
 

stevedore/tests/test_driver.py

@@ -13,12 +13,7 @@
 """Tests for stevedore.extension
 """
 
-try:
-    # For python 3.8 and later
-    import importlib.metadata as importlib_metadata
-except ImportError:
-    # For everyone else
-    import importlib_metadata
+import importlib.metadata as importlib_metadata
 
 from stevedore import driver
 from stevedore import exception

stevedore/tests/test_extension.py

@@ -13,16 +13,10 @@
 """Tests for stevedore.extension
 """
 
+import importlib.metadata as importlib_metadata
 import operator
 from unittest import mock
 
-try:
-    # For python 3.8 and later
-    import importlib.metadata as importlib_metadata
-except ImportError:
-    # For everyone else
-    import importlib_metadata
-
 from stevedore import exception
 from stevedore import extension
 from stevedore.tests import utils

stevedore/tests/test_sphinxext.py

@@ -12,12 +12,7 @@
 """Tests for the sphinx extension
 """
 
-try:
-    # For python 3.8 and later
-    import importlib.metadata as importlib_metadata
-except ImportError:
-    # For everyone else
-    import importlib_metadata
+import importlib.metadata as importlib_metadata
 
 from stevedore import extension
 from stevedore import sphinxext