storage.py: unbreak readonly_storage=True on windows

diff --git a/src/allmydata/storage.py b/src/allmydata/storage.py
index 13ef5347d0fd6eb3e3502e827e0bfb54aa2fc69e..66f66886391aeee7d7f0092881d4f93fb7ee544b 100644 (file)
--- a/src/allmydata/storage.py
+++ b/src/allmydata/storage.py
@@ -908,9 +908,9 @@ class StorageServer(service.MultiService, Referenceable):
         # returns None if it cannot be measured (windows)
         try:
             disk_avail = self.stat_disk(self.storedir)
+            disk_avail -= self.reserved_space
         except AttributeError:
-            return None
-        disk_avail -= self.reserved_space
+            disk_avail = None
         if self.readonly_storage:
             disk_avail = 0
         return disk_avail