DiscoveredPackage: "no results to fetch"

[tdruez]

From #70 (comment)

Some project error started to appear with the addition of multiprocessing, with the error message:no results to fetch

File "/opt/scancodeio/scanpipe/models.py", line 532, in save
    super().save(*args, **kwargs)
  File "/usr/local/lib/python3.9/site-packages/django/db/models/base.py", line 726, in save
    self.save_base(using=using, force_insert=force_insert,
  File "/usr/local/lib/python3.9/site-packages/django/db/models/base.py", line 763, in save_base
    updated = self._save_table(
  File "/usr/local/lib/python3.9/site-packages/django/db/models/base.py", line 868, in _save_table
    results = self._do_insert(cls._base_manager, using, fields, returning_fields, raw)
  File "/usr/local/lib/python3.9/site-packages/django/db/models/base.py", line 906, in _do_insert
    return manager._insert(
  File "/usr/local/lib/python3.9/site-packages/django/db/models/manager.py", line 85, in manager_method
    return getattr(self.get_queryset(), name)(*args, **kwargs)
  File "/usr/local/lib/python3.9/site-packages/django/db/models/query.py", line 1270, in _insert
    return query.get_compiler(using=using).execute_sql(returning_fields)
  File "/usr/local/lib/python3.9/site-packages/django/db/models/sql/compiler.py", line 1417, in execute_sql
    return [self.connection.ops.fetch_returned_insert_columns(cursor, self.returning_params)]
  File "/usr/local/lib/python3.9/site-packages/django/db/backends/base/operations.py", line 185, in fetch_returned_insert_columns
    return cursor.fetchone()
  File "/usr/local/lib/python3.9/site-packages/django/db/utils.py", line 97, in inner
    return func(*args, **kwargs)
  File "/usr/local/lib/python3.9/site-packages/django/db/utils.py", line 90, in __exit__
    raise dj_exc_value.with_traceback(traceback) from exc_value
  File "/usr/local/lib/python3.9/site-packages/django/db/utils.py", line 97, in inner
    return func(*args, **kwargs)

For some reason after an insert, the inserted object cannot be fetched.

See also https://code.djangoproject.com/ticket/20161

[tdruez]

This seems fixed with the latest improvements in the multiprocessing implementation.