New check method on models not documented in release notes

[Kevin Brown]

Django 1.7 adds a new check command for models that is called on the class. As far as I can tell, this is only mentioned (briefly) in the documentation for the check framework.

​https://docs.djangoproject.com/en/1.7/topics/checks/#field-model-and-manager-checks

If users create a model that has a method check, calling manage.py check will fail (because of the conflicting method names).

Traceback (most recent call last):
  File "manage.py", line 12, in <module>
    execute_from_command_line(sys.argv)
  File "/home/<>/.virtualenvs/<>/local/lib/python2.7/site-packages/django/core/management/__init__.py", line 427, in execute_from_command_line
    utility.execute()
  File "/home/<>/.virtualenvs/<>/local/lib/python2.7/site-packages/django/core/management/__init__.py", line 419, in execute
    self.fetch_command(subcommand).run_from_argv(self.argv)
  File "/home/<>/.virtualenvs/<>/local/lib/python2.7/site-packages/django/core/management/base.py", line 288, in run_from_argv
    self.execute(*args, **options.__dict__)
  File "/home/<>/.virtualenvs/<>/local/lib/python2.7/site-packages/django/core/management/base.py", line 337, in execute
    output = self.handle(*args, **options)
  File "/home/<>/.virtualenvs/<>/local/lib/python2.7/site-packages/django/core/management/commands/check.py", line 39, in handle
    self.check(app_configs=app_configs, tags=tags, display_num_errors=True)
  File "/home/<>/.virtualenvs/<>/local/lib/python2.7/site-packages/django/core/management/base.py", line 370, in check
    all_issues = checks.run_checks(app_configs=app_configs, tags=tags)
  File "/home/<>/.virtualenvs/<>/local/lib/python2.7/site-packages/django/core/checks/registry.py", line 59, in run_checks
    new_errors = check(app_configs=app_configs)
  File "/home/<>/.virtualenvs/<>/local/lib/python2.7/site-packages/django/core/checks/model_checks.py", line 16, in check_all_models
    if app_configs is None or model._meta.app_config in app_configs]
TypeError: unbound method check() must be called with [model name] instance as first argument (got nothing instead)

This is not mentioned in the release notes for Django 1.7 at all and worked fine in previous versions:

​https://docs.djangoproject.com/en/1.7/releases/1.7/

[loic84]

LGTM.

[Tim Graham <timograham@…>]

In 8905fcbda6854b5b7fdd8a1ee3277f8f1039e114:

Fixed #22526 -- Added note about check() method to 1.7 release notes.

Thanks kevin-brown for the report.

[Tim Graham <timograham@…>]

In 529ae6087c8e68587689de646960235e95c26cf0:

[1.7.x] Fixed #22526 -- Added note about check() method to 1.7 release notes.

Thanks kevin-brown for the report.

Backport of 8905fcbda6 from master