Fix string_field property

 - 'string_field' was missing from __all__
 - use operator.itemgetter instead of trivial getter function

debexpo/plugins/api.py

@@ -42,11 +42,13 @@ __all__ = ['importercmd',
            'QAPlugin',
            'PluginResult',
            'bool_field',
-           'int_field']
+           'int_field',
+           'string_field']
 
 import os.path
 import logging
 from inspect import getmembers, ismethod
+import operator
 
 from pylons import config
 # template rendering
@@ -147,13 +149,11 @@ def string_field(name):
     """
     Property for accessing a string item from the plugin result's dictionary.
     """
-    def fget(instance):
-        return instance.get(name, "")
 
     def fset(instance, value):
         instance[name] = value
 
-    return property(fget, fset, _fdel(name))
+    return property(operator.itemgetter(name), fset, _fdel(name))
 
 
 #