id	summary	reporter	owner	description	type	status	component	version	severity	resolution	keywords	cc	stage	has_patch	needs_docs	needs_tests	needs_better_patch	easy	ui_ux
30506	"Auto-reloading with StatReloader very intermittently throws ""ValueError: embedded null byte""."	Keryn Knight	Tom Forbes	"Raising this mainly so that it's tracked, as I have no idea how to reproduce it, nor why it's happening. It ultimately looks like a problem with Pathlib, which wasn't used prior to 2.2.

Stacktrace:
{{{
Traceback (most recent call last):
  File ""manage.py"" ...
    execute_from_command_line(sys.argv)
  File ""/Userz/kez/path/to/venv/lib/python3.6/site-packages/django/core/management/__init__.py"", line 381, in execute_from_command_line
    utility.execute()
  File ""/Userz/kez/path/to/venv/lib/python3.6/site-packages/django/core/management/__init__.py"", line 375, in execute
    self.fetch_command(subcommand).run_from_argv(self.argv)
  File ""/Userz/kez/path/to/venv/lib/python3.6/site-packages/django/core/management/base.py"", line 323, in run_from_argv
    self.execute(*args, **cmd_options)
  File ""/Userz/kez/path/to/venv/lib/python3.6/site-packages/django/core/management/commands/runserver.py"", line 60, in execute
    super().execute(*args, **options)
  File ""/Userz/kez/path/to/venv/lib/python3.6/site-packages/django/core/management/base.py"", line 364, in execute
    output = self.handle(*args, **options)
  File ""/Userz/kez/path/to/venv/lib/python3.6/site-packages/django/core/management/commands/runserver.py"", line 95, in handle
    self.run(**options)
  File ""/Userz/kez/path/to/venv/lib/python3.6/site-packages/django/core/management/commands/runserver.py"", line 102, in run
    autoreload.run_with_reloader(self.inner_run, **options)
  File ""/Userz/kez/path/to/venv/lib/python3.6/site-packages/django/utils/autoreload.py"", line 577, in run_with_reloader
    start_django(reloader, main_func, *args, **kwargs)
  File ""/Userz/kez/path/to/venv/lib/python3.6/site-packages/django/utils/autoreload.py"", line 562, in start_django
    reloader.run(django_main_thread)
  File ""/Userz/kez/path/to/venv/lib/python3.6/site-packages/django/utils/autoreload.py"", line 280, in run
    self.run_loop()
  File ""/Userz/kez/path/to/venv/lib/python3.6/site-packages/django/utils/autoreload.py"", line 286, in run_loop
    next(ticker)
  File ""/Userz/kez/path/to/venv/lib/python3.6/site-packages/django/utils/autoreload.py"", line 326, in tick
    for filepath, mtime in self.snapshot_files():
  File ""/Userz/kez/path/to/venv/lib/python3.6/site-packages/django/utils/autoreload.py"", line 342, in snapshot_files
    for file in self.watched_files():
  File ""/Userz/kez/path/to/venv/lib/python3.6/site-packages/django/utils/autoreload.py"", line 241, in watched_files
    yield from iter_all_python_module_files()
  File ""/Userz/kez/path/to/venv/lib/python3.6/site-packages/django/utils/autoreload.py"", line 103, in iter_all_python_module_files
    return iter_modules_and_files(modules, frozenset(_error_files))
  File ""/Userz/kez/path/to/venv/lib/python3.6/site-packages/django/utils/autoreload.py"", line 132, in iter_modules_and_files
    results.add(path.resolve().absolute())
  File ""/Users/kez/.pyenv/versions/3.6.2/lib/python3.6/pathlib.py"", line 1120, in resolve
    s = self._flavour.resolve(self, strict=strict)
  File ""/Users/kez/.pyenv/versions/3.6.2/lib/python3.6/pathlib.py"", line 346, in resolve
    return _resolve(base, str(path)) or sep
  File ""/Users/kez/.pyenv/versions/3.6.2/lib/python3.6/pathlib.py"", line 330, in _resolve
    target = accessor.readlink(newpath)
  File ""/Users/kez/.pyenv/versions/3.6.2/lib/python3.6/pathlib.py"", line 441, in readlink
    return os.readlink(path)
ValueError: embedded null byte
}}}

I did `print(path)` before `os.readlink(path)` in pathlib and ended up with:
{{{
/Users/kez
/Users/kez/.pyenv
/Users/kez/.pyenv/versions
/Users/kez/.pyenv/versions/3.6.2
/Users/kez/.pyenv/versions/3.6.2/lib
/Users/kez/.pyenv/versions/3.6.2/lib/python3.6
/Users/kez/.pyenv/versions/3.6.2/lib/python3.6/asyncio
/Users/kez/.pyenv/versions/3.6.2/lib/python3.6/asyncio/selector_events.py
/Users
}}}

- It always seems to be `/Users` which is last
- It may have already printed `/Users` as part of another `.resolve()` multiple times (that is, the order is not deterministic, and it may have traversed beyond `/Users` successfully many times during startup.
- I don't know where to begin looking for the rogue null byte, nor why it only exists sometimes.

Best guess I have is that there's a mountpoint in `/Users` to a samba share which may not have been connected to yet? I dunno.

- I have no idea if it's fixable without removing the use of pathlib (which tbh I think should happen anyway, because it's slow) and reverting to using `os.path.join` and friends. 
- I have no idea if it's fixed in a later Python version, but with no easy way to reproduce ... dunno how I'd check.
- I have no idea if it's something specific to my system (pyenv, OSX 10.11, etc)"	Bug	closed	Core (Management commands)	dev	Release blocker	fixed		Tom Forbes	Accepted	1	0	0	0	0	0