Add support for removing file format backends.

Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>

lib/newfol/filemanip.py

@@ -567,6 +567,13 @@ class FileStorage:
     def register_backend(klass, name, obj):
         klass.BACKENDS[name] = obj
 
+    @classmethod
+    def unregister_backend(klass, name):
+        try:
+            del klass.BACKENDS[name]
+        except KeyError:
+            pass
+
     @staticmethod
     def _canonicalize_transaction_types(types):
         if types is None:

test/testfilemanip.py

@@ -262,6 +262,12 @@ class PluggableBackendsTest(unittest.TestCase):
         self.assertEqual(len(recs), 1)
         self.assertEqual(recs[0].fields, ['a', 'b'])
 
+    def test_removing_backend(self):
+        FileStorage.register_backend('example', ExampleFile)
+        self.assertEqual(FileStorage.BACKENDS['example'], ExampleFile)
+        FileStorage.unregister_backend('example')
+        with self.assertRaises(KeyError):
+            FileStorage.BACKENDS['example']
 
 if __name__ == '__main__':
     unittest.main()