Fixed issues raised by new Pylint version 2.9

Details:

* Fixed new issue deprecated-class when importing from collections as a fallback
  on Python versions that do not yet have collections.abc.

* Fixed consider-using-with on an open/close sequence in test code by using with.

* Circumvented a pylint issue where it raises no-member on Python 3.9 when
  accessing argparse parsing result members. (see issue #1001)

Signed-off-by: Andreas Maier <andreas.r.maier@gmx.de>

docs/changes.rst

@@ -35,6 +35,8 @@ Released: not yet
   The function display_cim_objects(...) uses valuemapping_for_property() but
   specifies the default namespace as the target.  (See issue #995)
 
+* Fixed issues raised by new Pylint version 2.9.
+
 **Enhancements:**
 
 **Cleanup:**

pywbemtools/pywbemcli/_common.py

@@ -25,6 +25,7 @@
 try:
     from collections.abc import Sequence
 except ImportError:
+    # pylint: disable=deprecated-class
     from collections import Sequence
 
 import six

pywbemtools/pywbemlistener/_cmd_listener.py

@@ -425,6 +425,9 @@ def get_listeners(name=None):
         args = parse_listener_args(listener_args)
         if args:
             if name is None or args.name == name:
+                # pylint: disable=no-member
+                # Note: This is a workaround for Pylint raising no-member on
+                # Python 3.9 (see issue #1001)
                 logfile = get_logfile(args.logdir, args.name)
                 lis = ListenerProperties(
                     name=args.name, port=args.port, scheme=args.scheme,
@@ -433,6 +436,8 @@ def get_listeners(name=None):
                     indi_file=args.indi_file, indi_format=args.indi_format,
                     logfile=logfile,
                     pid=p.pid, created=datetime.fromtimestamp(p.create_time()))
+                # pylint: enable=no-member
+                # Note: End of workaround
                 ret.append(lis)
     return ret
 

tests/unit/pywbemcli/test_pywbem_server.py

@@ -549,7 +549,8 @@ def test_pysvr_connect_attrs(testcase, init_kwargs, exp_attrs):
 
     # Create temp fake file.
     # NOTE: We cannot use fixtures because we are using simplified_test_function
-    open(FAKE_PEM_PATH, 'a').close()
+    with open(FAKE_PEM_PATH, 'a'):
+        pass
 
     # connect and test connection results. Try block insures finally is
     # called.

tests/unit/utils.py

@@ -24,6 +24,7 @@
 try:
     from collections.abc import Mapping, Sequence
 except ImportError:
+    # pylint: disable=deprecated-class
     from collections import Mapping, Sequence
 try:
     from StringIO import StringIO  # Python 2
@@ -249,8 +250,7 @@ def execute_command(cmdname, args, env=None, stdin=None, verbose=False,
             rc = proc.returncode
 
     # Restore environment of current process
-    for name in saved_env:
-        value = saved_env[name]
+    for name, value in saved_env.items():
         if value is None:
             del os.environ[name]
         else: