Fix exception handling from response

The response class has a __bool__ method so checking 'if not response'
has a different meaning than the code intended.

Change-Id: I85f0f3642d752372f6aa33db296e26b2f81f5ee9

vmware_nsxlib/tests/unit/v3/mocks.py

@@ -90,6 +90,16 @@ class MockRequestsResponse(object):
     def json(self):
         return jsonutils.loads(self.content)
 
+    def __bool__(self):
+        """Returns True if :attr:`status_code` is less than 400.
+
+        This attribute checks if the status code of the response is between
+        400 and 600 to see if there was a client error or a server error. If
+        the status code, is between 200 and 400, this will return True. This
+        is **not** a check to see if the response code is ``200 OK``.
+        """
+        return self.status_code < 400
+
 
 class MockRequestSessionApi(object):
 

vmware_nsxlib/tests/unit/v3/nsxlib_testcase.py

@@ -278,7 +278,7 @@ class NsxClientTestCase(NsxLibTestCase):
             super(NsxClientTestCase.MockHTTPProvider, self).__init__()
             if isinstance(session_response, list):
                 self._session_responses = session_response
-            elif session_response:
+            elif session_response is not None:
                 self._session_responses = [session_response]
             else:
                 self._session_responses = None

vmware_nsxlib/v3/client.py

@@ -52,7 +52,9 @@ def get_http_error_details(response):
 
 
 def init_http_exception_from_response(response):
-    if not response:
+    if response is None or response:
+        # The response object has a __bool__ method that return True for
+        # status code under 400. In that case there is no need for exception
         return None
 
     error_details = get_http_error_details(response)