[fix] rmtree: Support non-writeable parent directory

Reuse more code from slapos.core to support case of parent directory
not writable.

src/zc/buildout/rmtree.py

@@ -16,6 +16,8 @@
 import shutil
 import os
 import doctest
+import errno
+import sys
 
 def rmtree (path):
     """
@@ -27,6 +29,8 @@ def rmtree (path):
 
     Also it tries to remove symlink itself if a symlink as passed as
     path argument.
+
+    Finally, it tries to make parent directory writable.
     >>> from tempfile import mkdtemp
 
     Let's make a directory ...
@@ -47,7 +51,11 @@ def rmtree (path):
 
     and make it unwriteable
 
-    >>> os.chmod (foo, 256) # 0400
+    >>> os.chmod (foo, 0o400)
+
+    and make parent dir unwritable
+
+    >>> os.chmod (d, 0o400)
 
     rmtree should be able to remove it:
 
@@ -90,7 +98,9 @@ def rmtree (path):
     >>> os.path.isdir (d)
     0
     """
-    def retry_writeable (func, path, exc):
+    def chmod_retry(func, failed_path, exc_info):
+        """Make sure the directories are executable and writable.
+        """
         if func is os.path.islink:
             os.unlink(path)
         elif func is os.lstat or func is os.open:
@@ -98,10 +108,33 @@ def rmtree (path):
                 raise
             os.unlink(path)
         else:
-            os.chmod(path, 0o600)
-            func(path)
+            # Depending on the Python version, the following items differ.
+            if sys.version_info >= (3, ):
+                expected_error_type = PermissionError
+                expected_func_tuple = (os.lstat, os.open)
+            else:
+                expected_error_type = OSError
+                expected_func_tuple = (os.listdir, )
+            e = exc_info[1]
+            if isinstance(e, expected_error_type):
+                if e.errno == errno.ENOENT:
+                    # because we are calling again rmtree on listdir errors, this path might
+                    # have been already deleted by the recursive call to rmtree.
+                    return
+                if e.errno == errno.EACCES:
+                    if func in expected_func_tuple:
+                        os.chmod(failed_path, 0o700)
+                        # corner case to handle errors in listing directories.
+                        # https://bugs.python.org/issue8523
+                        return shutil.rmtree(failed_path, onerror=chmod_retry)
+                    # If parent directory is not writable, we still cannot delete the file.
+                    # But make sure not to change the parent of the folder we are deleting.
+                    if failed_path != path:
+                        os.chmod(os.path.dirname(failed_path), 0o700)
+                        return func(failed_path)
+            raise
 
-    shutil.rmtree (path, onerror = retry_writeable)
+    shutil.rmtree(path, onerror=chmod_retry)
 
 def test_suite():
     return doctest.DocTestSuite()