Re: shutil.rmtree() fails when used in Fedora (rpm) "mock" environment

On 2024-10-24 08:33, Christian Buhtz via Python-list wrote:

Hello,
I am upstream maintainer of "Back In Time" [1] investigating an issue a
distro maintainer from Fedora reported [2] to me.
 On one hand Fedora seems to use a tool called "mock" to build packages
in a chroot environment.
On the other hand the test suite of "Back In Time" does read and write
to the real file system.
One test fails because a temporary directory is cleaned up using
shutil.rmtree(). Please see the output below.
 I am not familiar with Fedora and "mock". So I am not able to reproduce
this on my own.
It seems the Fedora maintainer also has no clue how to solve it or why
it happens.
 Can you please have a look (especially at the line "assert func is
os.lstat").
Maybe you have an idea what is the intention behind this error raised by
an "assert" statement inside "shutil.rmtree()".
 Thanks in advance,
Christian Buhtz
 [1] -- <https://github.com/bit-team/backintime>
[2] -- <https://github.com/bit-team/backintime/issues/1911>
 __________________________ General.test_ctor_defaults
__________________________
self = <test.test_uniquenessset.General testMethod=test_ctor_defaults>
      def test_ctor_defaults(self):
          """Default values in constructor."""

      with TemporaryDirectory(prefix='bit.') as temp_name:

test/test_uniquenessset.py:47:
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
_ _ _ _
/usr/lib64/python3.13/tempfile.py:946: in __exit__
      self.cleanup()
/usr/lib64/python3.13/tempfile.py:950: in cleanup
      self._rmtree(self.name, ignore_errors=self._ignore_cleanup_errors)
/usr/lib64/python3.13/tempfile.py:930: in _rmtree
      _shutil.rmtree(name, onexc=onexc)
/usr/lib64/python3.13/shutil.py:763: in rmtree
      _rmtree_safe_fd(stack, onexc)
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
_ _ _ _
stack = []
onexc = <function TemporaryDirectory._rmtree.<locals>.onexc at
0xffffb39bc860>
      def _rmtree_safe_fd(stack, onexc):
          # Each stack item has four elements:
          # * func: The first operation to perform: os.lstat, os.close or
os.rmdir.
          #   Walking a directory starts with an os.lstat() to detect
symlinks; in
          #   this case, func is updated before subsequent operations and
passed to
          #   onexc() if an error occurs.
          # * dirfd: Open file descriptor, or None if we're processing the
top-level
          #   directory given to rmtree() and the user didn't supply
dir_fd.
          # * path: Path of file to operate upon. This is passed to
onexc() if an
          #   error occurs.
          # * orig_entry: os.DirEntry, or None if we're processing the
top-level
          #   directory given to rmtree(). We used the cached stat() of
the entry to
          #   save a call to os.lstat() when walking subdirectories.
          func, dirfd, path, orig_entry = stack.pop()
          name = path if orig_entry is None else orig_entry.name
          try:
              if func is os.close:
                  os.close(dirfd)
                  return
              if func is os.rmdir:
                  os.rmdir(name, dir_fd=dirfd)
                  return
               # Note: To guard against symlink races, we use the standard
              # lstat()/open()/fstat() trick.

          assert func is os.lstat

E           AssertionError
/usr/lib64/python3.13/shutil.py:663: AssertionError
 

What does "mock" do?
func should be either os.close, os.rmdir or os.lstat.
If mock is somehow replacing one of those functions, then it might break the code.