Make str() of Account() be its name

So we can simply hand an account instance to error messages rather than
having to call Account().getname() all the time.

This is not used yet.

Signed-off-by: Sebastian Spaeth <Sebastian@SSpaeth.de>
Signed-off-by: Nicolas Sebrecht <nicolas.s-dev@laposte.net>

offlineimap/accounts.py

@@ -125,6 +125,9 @@ class Account(CustomConfig.ConfigHelperMixin):
     def getname(self):
         return self.name
 
+    def __str__(self):
+        return self.name
+
     def getsection(self):
         return 'Account ' + self.getname()