Make APIVersion's null check more pythonic

Our current APIVersion object has an is_null method to check when the
version instance is null (major=0 and minor=0).

While this works it is not very pythonic, since you have to write
expressions such as:

 if not min_version and not max_version:
     return True
 elif ((min_version and max_version) and
       max_version.is_null() and min_version.is_null()):
     return True

This patch removes the is_null method and instead implements the truth
value testing to simplify expressions and make code more pythonic.

So previous code would just look like:

 if not min_version and not max_version:
     return True

Because this will work with min_version being None or being an
APIVersion instance with major=0 and minor=0.

Change-Id: I7497c5dc940c1e726507117cadbad232d8c1d80d

1 files changed, 3 insertions, 3 deletions

diff --git a/cinderclient/exceptions.py b/cinderclient/exceptions.py
index 6d9e707..23b31b1 100644
--- a/cinderclient/exceptions.py
+++ b/cinderclient/exceptions.py
@@ -34,19 +34,19 @@ class UnsupportedAttribute(AttributeError):
     """
 
     def __init__(self, argument_name, start_version, end_version):
-        if not start_version.is_null() and not end_version.is_null():
+        if start_version and end_version:
             self.message = (
                 "'%(name)s' argument is only allowed for microversions "
                 "%(start)s - %(end)s." % {"name": argument_name,
                                           "start": start_version.get_string(),
                                           "end": end_version.get_string()})
-        elif not start_version.is_null():
+        elif start_version:
             self.message = (
                 "'%(name)s' argument is only allowed since microversion "
                 "%(start)s." % {"name": argument_name,
                                 "start": start_version.get_string()})
 
-        elif not end_version.is_null():
+        elif end_version:
             self.message = (
                 "'%(name)s' argument is not allowed after microversion "
                 "%(end)s." % {"name": argument_name,