IntegrityError at /accounts/register/: duplicate key value violates unique constraint "front_user_username_key"

[The-Compiler]

Ich habe in letzter Zeit (24.7. bzw. 13.8.) zwei unhandled exceptions via Mail bekommen, die ich mir nicht erklären kann. Bei beiden heisst es nach einem POST auf http://studentenportal.ch/accounts/register/:

Traceback (most recent call last):
  File "/usr/local/lib/python3.7/site-packages/django/db/backends/utils.py", line 84, in _execute
    return self.cursor.execute(sql, params)

The above exception (duplicate key value violates unique constraint "front_user_username_key"
DETAIL:  Key (username)=(redacted.redacted) already exists.
) was the direct cause of the following exception:
  File "/usr/local/lib/python3.7/site-packages/django/core/handlers/exception.py", line 47, in inner
    response = get_response(request)
  File "/usr/local/lib/python3.7/site-packages/django/core/handlers/base.py", line 181, in _get_response
    response = wrapped_callback(request, *callback_args, **callback_kwargs)
  File "/usr/local/lib/python3.7/site-packages/django/views/generic/base.py", line 70, in view
    return self.dispatch(request, *args, **kwargs)
  File "/usr/local/lib/python3.7/site-packages/django/utils/decorators.py", line 43, in _wrapper
    return bound_method(*args, **kwargs)
  File "/usr/local/lib/python3.7/site-packages/django/views/decorators/debug.py", line 89, in sensitive_post_parameters_wrapper
    return view(request, *args, **kwargs)
  File "/usr/local/lib/python3.7/site-packages/registration/views.py", line 53, in dispatch
    return super().dispatch(request, *args, **kwargs)
  File "/usr/local/lib/python3.7/site-packages/django/views/generic/base.py", line 98, in dispatch
    return handler(request, *args, **kwargs)
  File "/usr/local/lib/python3.7/site-packages/django/views/generic/edit.py", line 142, in post
    return self.form_valid(form)
  File "/usr/local/lib/python3.7/site-packages/registration/views.py", line 56, in form_valid
    new_user = self.register(form)
  File "/usr/local/lib/python3.7/site-packages/registration/backends/default/views.py", line 100, in register
    request=self.request,
  File "/usr/local/lib/python3.7/site-packages/registration/models.py", line 184, in create_inactive_user
    new_user.save()
  File "/usr/local/lib/python3.7/site-packages/django/contrib/auth/base_user.py", line 67, in save
    super().save(*args, **kwargs)
  File "/usr/local/lib/python3.7/site-packages/django/db/models/base.py", line 740, in save
    force_update=force_update, update_fields=update_fields)
  File "/usr/local/lib/python3.7/site-packages/django/db/models/base.py", line 778, in save_base
    force_update, using, update_fields,
  File "/usr/local/lib/python3.7/site-packages/django/db/models/base.py", line 881, in _save_table
    results = self._do_insert(cls._base_manager, using, fields, returning_fields, raw)
  File "/usr/local/lib/python3.7/site-packages/django/db/models/base.py", line 921, in _do_insert
    using=using, raw=raw,
  File "/usr/local/lib/python3.7/site-packages/django/db/models/manager.py", line 85, in manager_method
    return getattr(self.get_queryset(), name)(*args, **kwargs)
  File "/usr/local/lib/python3.7/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/python3.7/site-packages/django/db/models/sql/compiler.py", line 1416, in execute_sql
    cursor.execute(sql, params)
  File "/usr/local/lib/python3.7/site-packages/django/db/backends/utils.py", line 66, in execute
    return self._execute_with_wrappers(sql, params, many=False, executor=self._execute)
  File "/usr/local/lib/python3.7/site-packages/django/db/backends/utils.py", line 75, in _execute_with_wrappers
    return executor(sql, params, many, context)
  File "/usr/local/lib/python3.7/site-packages/django/db/backends/utils.py", line 84, in _execute
    return self.cursor.execute(sql, params)
  File "/usr/local/lib/python3.7/site-packages/django/db/utils.py", line 90, in __exit__
    raise dj_exc_value.with_traceback(traceback) from exc_value
  File "/usr/local/lib/python3.7/site-packages/django/db/backends/utils.py", line 84, in _execute
    return self.cursor.execute(sql, params)

Exception Type: IntegrityError at /accounts/register/
Exception Value: duplicate key value violates unique constraint "front_user_username_key"
DETAIL:  Key (username)=(redacted.redacted) already exists.

aber wir fangen das eigentlich schon ab:

web/apps/front/forms.py

Lines 48 to 50 in f44e535

	# Ensure that user with this email does not exist yet
	if User.objects.filter(email__iexact=email).exists():
	raise forms.ValidationError("Benutzer mit dieser E-Mail existiert bereits.")

und ich kann das Problem auch nicht reproduzieren - mit denselben Daten wie im Mail kriege ich wie erwartet direkt im Browser eine Meldung. Der User existiert tatsächlich mit der exakt selben Mail schon in der Datenbank.

@dbrgn du hast die Validierung damals™ in b6c0c77 implementiert - kannst du dir da irgend nen Reim daraus machen?

[dbrgn]

Beim Check wird die E-Mail geprüft, bei der Fehlermeldung geht es um den Username. Der wird irgendwie von der E-Mail abgeleitet, oder? Ev gibt's User, wo der Username nicht (mehr) zur E-Mail passt.