kadi find_attitude crashes django dev server without --noreload flag

[taldcroft]

With the py3-server branch, when trying to solve for attitude with find_attitude using the django runserver, one gets a hard crash that is not caught by django debug (see below). I don't know what is going on except that it does not happen with python manage.py runserver --noreload. This may be related to some threading (or non-threadsafe code), because even with --noreload one gets this warning: WARNING: signal only works in main thread. Using --nothreading makes that go away.

We'll see if this affects operation on the Apache/mod_wsgi server.

WARNING: imaging routines will not be available, 
failed to import sherpa.image.ds9_backend due to 
'RuntimeErr: DS9Win unusable: Could not find ds9 on your PATH'
Traceback (most recent call last):
  File "manage.py", line 11, in <module>
    execute_from_command_line(sys.argv)
  File "/export/tom/miniconda3/envs/ska3-django3/lib/python3.6/site-packages/django/core/management/__init__.py", line 401, in execute_from_command_line
    utility.execute()
  File "/export/tom/miniconda3/envs/ska3-django3/lib/python3.6/site-packages/django/core/management/__init__.py", line 395, in execute
    self.fetch_command(subcommand).run_from_argv(self.argv)
  File "/export/tom/miniconda3/envs/ska3-django3/lib/python3.6/site-packages/django/core/management/base.py", line 328, in run_from_argv
    self.execute(*args, **cmd_options)
  File "/export/tom/miniconda3/envs/ska3-django3/lib/python3.6/site-packages/django/core/management/commands/runserver.py", line 60, in execute
    super().execute(*args, **options)
  File "/export/tom/miniconda3/envs/ska3-django3/lib/python3.6/site-packages/django/core/management/base.py", line 369, in execute
    output = self.handle(*args, **options)
  File "/export/tom/miniconda3/envs/ska3-django3/lib/python3.6/site-packages/django/core/management/commands/runserver.py", line 95, in handle
    self.run(**options)
  File "/export/tom/miniconda3/envs/ska3-django3/lib/python3.6/site-packages/django/core/management/commands/runserver.py", line 102, in run
    autoreload.run_with_reloader(self.inner_run, **options)
  File "/export/tom/miniconda3/envs/ska3-django3/lib/python3.6/site-packages/django/utils/autoreload.py", line 599, in run_with_reloader
    start_django(reloader, main_func, *args, **kwargs)
  File "/export/tom/miniconda3/envs/ska3-django3/lib/python3.6/site-packages/django/utils/autoreload.py", line 584, in start_django
    reloader.run(django_main_thread)
  File "/export/tom/miniconda3/envs/ska3-django3/lib/python3.6/site-packages/django/utils/autoreload.py", line 299, in run
    self.run_loop()
  File "/export/tom/miniconda3/envs/ska3-django3/lib/python3.6/site-packages/django/utils/autoreload.py", line 305, in run_loop
    next(ticker)
  File "/export/tom/miniconda3/envs/ska3-django3/lib/python3.6/site-packages/django/utils/autoreload.py", line 345, in tick
    for filepath, mtime in self.snapshot_files():
  File "/export/tom/miniconda3/envs/ska3-django3/lib/python3.6/site-packages/django/utils/autoreload.py", line 361, in snapshot_files
    for file in self.watched_files():
  File "/export/tom/miniconda3/envs/ska3-django3/lib/python3.6/site-packages/django/utils/autoreload.py", line 260, in watched_files
    yield from iter_all_python_module_files()
  File "/export/tom/miniconda3/envs/ska3-django3/lib/python3.6/site-packages/django/utils/autoreload.py", line 105, in iter_all_python_module_files
    return iter_modules_and_files(modules, frozenset(_error_files))
  File "/export/tom/miniconda3/envs/ska3-django3/lib/python3.6/site-packages/django/utils/autoreload.py", line 118, in iter_modules_and_files
    if module.__name__ == '__main__':
  File "/export/tom/miniconda3/envs/ska3-django3/lib/python3.6/site-packages/py/_apipkg.py", line 171, in __getattribute__
    return getattr(getmod(), name)
  File "/export/tom/miniconda3/envs/ska3-django3/lib/python3.6/site-packages/py/_error.py", line 44, in __getattr__
    raise AttributeError(name)
AttributeError: __name__

[taldcroft]

Also worth noting that this occurs only on linux (CentOS-7) and not on MacOSX.