Improve error handling for file_path.rmtree()

client/utils/file_path.py

 # Copyright 2013 The LUCI Authors. All rights reserved.
 # Use of this source code is governed under the Apache License, Version 2.0
 # that can be found in the LICENSE file.
 
 """Provides functions: get_native_path_case(), isabs() and safe_join().
 
 This module assumes that filesystem is not changing while current process
 is running and thus it caches results of functions that depend on FS state.
 """
 
@@ skipping 1148 matching lines @@
       time.sleep((i+1)*2)
   else:
     processes = get_processes()
     if processes:
       sys.stderr.write('Failed to terminate processes.\n')
       raise errors[0][2][0], errors[0][2][1], errors[0][2][2]
 
   # Now that annoying processes in root are evicted, try again.
   errors = []
   fs.rmtree(root, onerror=lambda *args: errors.append(args))
-  if errors:
-    # There's no hope.
+  if errors and fs.exists(root):

[Vadim Sh., 2017/06/13 20:49:01]

as far as I can tell, this code path is not hit on Linux due to 'raise' on line
1119, so it's not the entire fix

+    # There's no hope: the directory was tried to be removed 4 times. Give up
+    # and raise an exception.
     sys.stderr.write(
         'Failed to delete %s. The following files remain:\n' % root)
-    for _, path, _ in errors:
+    # The same path may be listed multiple times.
+    for path in sorted(set(path for _, path, _ in errors)):
       sys.stderr.write('- %s\n' % path)
     raise errors[0][2][0], errors[0][2][1], errors[0][2][2]
   return False