add some logging

distem/__init__.py

 import json
 import copy
+import logging
 import requests
 
 
 class Distem:
-    def __init__(self, serveraddr="localhost", port=4567):
+    def __init__(self, *,  serveraddr="localhost", port=4567):
         self.serveraddr = serveraddr
         self.port = port
         self.client = requests.Session()
@@ -15,10 +16,10 @@ class Distem:
 
 
         Args:
-            name(str) The name of the virtual network (unique) address(str) The
-            address (CIDR format: 10.0.8.0/24) the virtual network will work
-              with options(dict) used to store vxlan_id and number of PNODES
-              (should not be used directly)
+            name (str): The name of the virtual network (unique) address(str) The
+            addres (str): address in CIDR format (e.g 10.0.8.0/24)
+            opts (dict): used to store vxlan_id and number of PNODES
+                (should not be used directly)
 
         Returns:
             {dict} The virtual network description
@@ -119,31 +120,30 @@ class Distem:
 
         return self.post_json("/vnodes/%s" % (name), data=data)
 
-    def vnode_start(self, vnodename):
-        """
-        Start a virtual node.
+    def vnode_start(self, vnodename, *, async=False):
+        """Start a virtual node.
 
-            A physical node (that have enought physical resources (CPU,...))
-            will be automatically allocated if there is none set as +host+ at
-            the moment The filesystem archive will be copied on the hosting
-            physical node. A filesystem image *must* have been set (see
-            {#vnode_create} or {#vfilesystem_create}/{#vfilesystem_update}).
+        A physical node (that have enough physical resources (CPU,...))
+        will be automatically allocated if there is none set as +host+ at
+        the moment The filesystem archive will be copied on the hosting
+        physical node. A filesystem image *must* have been set (see
+        {#vnode_create} or {#vfilesystem_create}/{#vfilesystem_update}).
 
 
         Args:
-            vnodename(str) The name of the virtual node
-            async(Boolean) Asynchronious mode, check virtual node status to know
-              when node is configured (see {#vnode_info})
+            vnodename (str): The name of the virtual node
+            async (bool): Asynchronious mode, check virtual node status to know
+                when node is configured (see {#vnode_info})
 
         Returns:
-            {dict} The virtual node description
+            dict of the virtual node description
               see :desc:`resources description<>`
         """
 
         desc = {
             "desc": {"name": str(vnodename), "status": "RUNNING"},
             "type": "update",
-            "async": False,
+            "async": async,
         }
 
         return self.put_json("/vnodes/%s" % (str(vnodename)), data=desc)
@@ -786,6 +786,7 @@ class Distem:
         )
 
     def raw_request(self, method, route, data):
+        logging.debug("method=%s, route=%s, data=%s", method, route, data)
         result = ""
         _data = copy.deepcopy(data)
         for key, value in data.items():
@@ -803,4 +804,5 @@ class Distem:
                 result = response.text
             return result
         else:
-            raise Exception(response.headers["X-Application-Error-Code"])
+            err = response.headers.get("X-Application-Error-Code", "Unknown error")
+            raise Exception(err)