Add API code values to confluent messages

When a message is used that would raise an exception in a singleton
case, make available the appropriate apicode in contexts that would be
relevant (namely multi-node operations and all asynchttp).

confluent_server/confluent/messages.py

@@ -59,6 +59,7 @@ def _htmlify_structure(indict):
 
 
 class ConfluentMessage(object):
+    apicode = 200
     readonly = False
     defaultvalue = ''
     defaulttype = 'text'
@@ -174,6 +175,8 @@ class ConfluentMessage(object):
 
 
 class ConfluentNodeError(object):
+    apicode = 500
+
     def __init__(self, node, errorstr):
         self.node = node
         self.error = errorstr
@@ -191,15 +194,20 @@ class ConfluentNodeError(object):
 
 
 class ConfluentTargetTimeout(ConfluentNodeError):
+    apicode = 504
+
     def __init__(self, node, errstr='timeout'):
         self.node = node
         self.error = errstr
 
+
     def strip_node(self, node):
         raise exc.TargetEndpointUnreachable(self.error)
 
 
 class ConfluentTargetNotFound(ConfluentNodeError):
+    apicode = 404
+
     def __init__(self, node, errorstr='not found'):
         self.node = node
         self.error = errorstr
@@ -209,6 +217,7 @@ class ConfluentTargetNotFound(ConfluentNodeError):
 
 
 class ConfluentTargetInvalidCredentials(ConfluentNodeError):
+    apicode = 502
     def __init__(self, node):
         self.node = node
         self.error = 'bad credentials'