[Bug #220993; may also fix bug #479469] Fix flakiness when old

  installations are present, by always unlinking the destination file
  before copying to it.  Without the unlink(), the copied file remains
  owned by its previous UID, causing the subsequent chmod() to fail.

Bugfix candidate, though it may cause changes on platforms where
  file ownership behaves differently.

diff --git a/Lib/distutils/file_util.py b/Lib/distutils/file_util.py
index 526e4cf593f59404f67f6c0b28d850e513684575..14772fb74aadadd36d76f42f80dea3ad6e0fe650 100644 (file)
--- a/Lib/distutils/file_util.py
+++ b/Lib/distutils/file_util.py
@@ -36,6 +36,13 @@ def _copy_file_contents (src, dst, buffer_size=16*1024):
             raise DistutilsFileError, \
                   "could not open '%s': %s" % (src, errstr)
 
+        if os.path.exists(dst):
+            try:
+                os.unlink(dst)
+            except os.error, (errno, errstr):
+                raise DistutilsFileError, \
+                      "could not delete '%s': %s" % (dst, errstr)
+        
         try:
             fdst = open(dst, 'wb')
         except os.error, (errno, errstr):