Use httplib constants for http status codes

The httplib (py2) and http.client (py3) have nice constants for all
the standard HTTP status codes. This patch changes the exception
module to make use of those.

Change-Id: I67d3717dca5aecf3c8b36f5b69f1ca659c0b08b1

keystone/exception.py

@@ -15,6 +15,7 @@
 from oslo_log import log
 from oslo_utils import encodeutils
 import six
+from six.moves import http_client
 
 import keystone.conf
 from keystone.i18n import _, _LW
@@ -84,8 +85,8 @@ class ValidationError(Error):
                        " The server could not comply with the request"
                        " since it is either malformed or otherwise"
                        " incorrect. The client is assumed to be in error.")
-    code = 400
-    title = 'Bad Request'
+    code = int(http_client.BAD_REQUEST)
+    title = http_client.responses[http_client.BAD_REQUEST]
 
 
 class URLValidationError(ValidationError):
@@ -129,8 +130,8 @@ class ValidationTimeStampError(Error):
                        " The server could not comply with the request"
                        " since it is either malformed or otherwise"
                        " incorrect. The client is assumed to be in error.")
-    code = 400
-    title = 'Bad Request'
+    code = int(http_client.BAD_REQUEST)
+    title = http_client.responses[http_client.BAD_REQUEST]
 
 
 class InvalidOperatorError(ValidationError):
@@ -144,8 +145,8 @@ class ValidationExpirationError(Error):
                        " The server could not comply with the request"
                        " since it is either malformed or otherwise"
                        " incorrect. The client is assumed to be in error.")
-    code = 400
-    title = 'Bad Request'
+    code = int(http_client.BAD_REQUEST)
+    title = http_client.responses[http_client.BAD_REQUEST]
 
 
 class StringLengthExceeded(ValidationError):
@@ -160,15 +161,15 @@ class ValidationSizeError(Error):
                        " could not comply with the request because"
                        " the attribute size is invalid (too large)."
                        " The client is assumed to be in error.")
-    code = 400
-    title = 'Bad Request'
+    code = int(http_client.BAD_REQUEST)
+    title = http_client.responses[http_client.BAD_REQUEST]
 
 
 class CircularRegionHierarchyError(Error):
     message_format = _("The specified parent region %(parent_region_id)s "
                        "would create a circular region hierarchy.")
-    code = 400
-    title = 'Bad Request'
+    code = int(http_client.BAD_REQUEST)
+    title = http_client.responses[http_client.BAD_REQUEST]
 
 
 class ForbiddenNotSecurity(Error):
@@ -179,8 +180,8 @@ class ForbiddenNotSecurity(Error):
 
     """
 
-    code = 403
-    title = 'Forbidden'
+    code = int(http_client.FORBIDDEN)
+    title = http_client.responses[http_client.FORBIDDEN]
 
 
 class PasswordVerificationError(ForbiddenNotSecurity):
@@ -249,8 +250,8 @@ class SecurityError(Error):
 
 class Unauthorized(SecurityError):
     message_format = _("The request you have made requires authentication.")
-    code = 401
-    title = 'Unauthorized'
+    code = int(http_client.UNAUTHORIZED)
+    title = http_client.responses[http_client.UNAUTHORIZED]
 
 
 class InsufficientAuthMethods(Error):
@@ -302,8 +303,8 @@ class AdditionalAuthRequired(AuthPluginException):
 class Forbidden(SecurityError):
     message_format = _("You are not authorized to perform the"
                        " requested action.")
-    code = 403
-    title = 'Forbidden'
+    code = int(http_client.FORBIDDEN)
+    title = http_client.responses[http_client.FORBIDDEN]
 
 
 class ForbiddenAction(Forbidden):
@@ -330,8 +331,8 @@ class InvalidDomainConfig(Forbidden):
 
 class NotFound(Error):
     message_format = _("Could not find: %(target)s.")
-    code = 404
-    title = 'Not Found'
+    code = int(http_client.NOT_FOUND)
+    title = http_client.responses[http_client.NOT_FOUND]
 
 
 class EndpointNotFound(NotFound):
@@ -460,8 +461,8 @@ class ConfigRegistrationNotFound(Exception):
 class Conflict(Error):
     message_format = _("Conflict occurred attempting to store %(type)s -"
                        " %(details)s.")
-    code = 409
-    title = 'Conflict'
+    code = int(http_client.CONFLICT)
+    title = http_client.responses[http_client.CONFLICT]
 
 
 class UnexpectedError(SecurityError):
@@ -483,8 +484,8 @@ class UnexpectedError(SecurityError):
         return super(UnexpectedError, self)._build_message(
             message or self.debug_message_format, **kwargs)
 
-    code = 500
-    title = 'Internal Server Error'
+    code = int(http_client.INTERNAL_SERVER_ERROR)
+    title = http_client.responses[http_client.INTERNAL_SERVER_ERROR]
 
 
 class TrustConsumeMaximumAttempt(UnexpectedError):
@@ -528,15 +529,15 @@ class AssignmentTypeCalculationError(UnexpectedError):
 class NotImplemented(Error):
     message_format = _("The action you have requested has not"
                        " been implemented.")
-    code = 501
-    title = 'Not Implemented'
+    code = int(http_client.NOT_IMPLEMENTED)
+    title = http_client.responses[http_client.NOT_IMPLEMENTED]
 
 
 class Gone(Error):
     message_format = _("The service you have requested is no"
                        " longer available on this server.")
-    code = 410
-    title = 'Gone'
+    code = int(http_client.GONE)
+    title = http_client.responses[http_client.GONE]
 
 
 class ConfigFileNotFound(UnexpectedError):