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.

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

docs/changes.rst

@@ -27,6 +27,8 @@ 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

@@ -31,6 +31,7 @@
 try:
     from collections.abc import Sequence
 except ImportError:
+    # pylint: disable=deprecated-class
     from collections import Sequence
 
 import six

tests/unit/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

@@ -159,8 +159,7 @@ def execute_pywbemcli(args, env=None, stdin=None, verbose=None, condition=True):
     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: