fileutil: make the error behaviour of replace_file on Unix more similar to Windows.

Signed-off-by: Daira Hopwood <daira@jacaranda.org>

diff --git a/src/allmydata/util/fileutil.py b/src/allmydata/util/fileutil.py
index 26943212bde4b6870e96e825a39b572992af4885..133d22710e653dded221b668f30ec2062d9d3e3a 100644 (file)
--- a/src/allmydata/util/fileutil.py
+++ b/src/allmydata/util/fileutil.py
@@ -615,6 +615,8 @@ else:
         precondition_abspath(replacement_path)
         precondition_abspath(backup_path)
 
+        if not os.path.exists(replacement_path):
+            raise ConflictError("Replacement file not found: %r" % (replacement_path,))
         try:
             os.rename(replaced_path, backup_path)
             rename_no_overwrite(replacement_path, replaced_path)