Added ServerWarning class and its base class Warning

Details:

* There are cases when pywbem needs to tolerate incorrect WBEM server
  behavior, but still needs to surface it. This change adds a ServerWarning
  class for this purpose. It is derived from a new base class Warning.

* The new base class Warning is derived from both pywbem.Error and the
  built-in Python Warning class, in order to pick up both behaviors.

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

docs/changes.rst

@@ -395,6 +395,10 @@ This version contains all fixes up to pywbem 0.12.4.
 * Improved the quality of any `ParseError` exception messages when the SAX
   parser detects errors in CIM-XML responses. See issue #1438.
 
+* Added a `ServerWarning` class and its base class `Warning`. The new
+  `ServerWarning` is raised in cases when the WBEM server exhibits some
+  incorrect behavior that is tolerated by pywbem.
+
 **Cleanup:**
 
 * Moved class `NocaseDict` into its own module (Issue #848).

pywbem/exceptions.py

@@ -19,12 +19,15 @@
 the WBEM client library API.
 """
 
+import six
+
 from .cim_constants import _statuscode2name, _statuscode2string
 
 # This module is meant to be safe for 'import *'.
 
 __all__ = ['Error', 'ConnectionError', 'AuthError', 'HTTPError', 'TimeoutError',
-           'VersionError', 'ParseError', 'CIMError']
+           'VersionError', 'ParseError', 'CIMError', 'Warning',
+           'ServerWarning']
 
 
 class Error(Exception):
@@ -352,3 +355,18 @@ def __str__(self):
             self.status_code, self.status_code_name, self.status_description,
             inst_str, self.conn_str)
         return ret_str
+
+
+class Warning(Error, six.moves.builtins.Warning):
+    """
+    Base class for pywbem specific warnings.
+    """
+    pass
+
+
+class ServerWarning(Warning):
+    """
+    This warning indicates an issue with the WBEM server that has been
+    tolerated by pywbem.
+    """
+    pass

testsuite/test_exceptions.py

@@ -10,7 +10,7 @@
 import pytest
 
 from pywbem import Error, ConnectionError, AuthError, HTTPError, TimeoutError,\
-    ParseError, VersionError, CIMError, CIMInstance
+    ParseError, VersionError, CIMError, Warning, ServerWarning, CIMInstance
 
 # Test connection ID used for showing connection information in exception
 # messages
@@ -68,12 +68,15 @@ def _assert_connection(exc, conn_id_kwarg, exp_conn_str):
     TimeoutError,
     ParseError,
     VersionError,
+    Warning,
+    ServerWarning,
 ], scope='module')
 def simple_class(request):
     """
-    Fixture representing variations of the simple exception classes.
+    Fixture representing variations of the simple exception and warning
+    classes.
 
-    Returns the exception class.
+    Returns the exception or warning class.
     """
     return request.param
 
@@ -88,7 +91,7 @@ def simple_class(request):
 def simple_args(request):
     """
     Fixture representing variations of positional init arguments for the simple
-    exception classes.
+    exception or warning classes.
 
     Returns a tuple of positional arguments for initializing an exception
     object.
@@ -105,7 +108,8 @@ def simple_args(request):
 def conn_info(request):
     """
     Fixture representing variations for the conn_id keyword argument for all
-    exception classes, and the corresponding expected connection info string.
+    exception and warning classes, and the corresponding expected connection
+    info string.
 
     Returns a tuple of:
     * conn_id_kwarg: dict with the 'conn_id' keyword argument. May be empty.
@@ -117,7 +121,10 @@ def conn_info(request):
 def test_simple(simple_class, simple_args, conn_info):
     # pylint: disable=redefined-outer-name
     """
-    Test the simple exception classes.
+    Test the simple exception and warning classes.
+
+    Note, the Python `Warning` class is derived from the `Exception` class and
+    thus can be treated like exception classes.
     """
 
     conn_id_kwarg, exp_conn_str = conn_info