Merge pull request #23 (error fixes)

This improves the RobotError exception so that repr() and str() perform
more like people are used to.

Also this adds a .format() that I forgot in
bbae95a.

Thanks to @nh2 for these fixes.

hetzner/__init__.py

@@ -1,14 +1,9 @@
 class RobotError(Exception):
     def __init__(self, message, status=None):
-        self.message = message
+        formattedMessage = message if status is None else "{0} ({1})".format(message, status)
+        super(Exception, self).__init__(formattedMessage)
         self.status = status
 
-    def __str__(self):
-        if self.status is None:
-            return self.message
-        else:
-            return "{0} ({1})".format(self.message, self.status)
-
 
 class ManualReboot(Exception):
     pass

hetzner/robot.py

@@ -86,7 +86,7 @@ def login(self, user=None, passwd=None, force=False):
         if self.user.startswith("#ws+"):
             raise WebRobotError("The user {0} is a dedicated web service user "
                                 "and cannot be used for scraping the web user "
-                                "interface.")
+                                "interface.".format(self.user))
 
         # This is primarily for getting a first session cookie.
         response = self.request('/login', xhr=False)