**Description**

function test_cycle will be collected by pytest if this function is imported in a user-defined test.
Such an error will be emitted as pytest will treat it as a test.
```
test setup failed
file /opt/conda/lib/python3.8/site-packages/airflow/utils/dag_cycle_tester.py, line 27
  def test_cycle(dag):
E       fixture 'dag' not found
>       available fixtures: cache, capfd, capfdbinary, caplog, capsys, capsysbinary, doctest_namespace, monkeypatch, pytestconfig, record_property, record_testsuite_property, record_xml_attribute, recwarn, tmp_path, tmp_path_factory, tmpdir, tmpdir_factory
>       use 'pytest --fixtures [testpath]' for help on them.

```

**Use case / motivation**
This can be simply "fixed" by renaming this function to check_cycle although the user can do it upon importing this function.
This change by airflow will reduce the amount of surprise received by the end-user, and save a large number of debugging hours. 

**Are you willing to submit a PR?**
The changeset is too small to worth the trouble for a PR. 
airflow/models/dagbag.py
return []
            except OperationalError:
                raise
            except Exception:  
                return [(dag.fileloc, traceback.format_exc(limit=-self.dagbag_import_error_traceback_depth))]
        
        
        
        for attempt in run_with_db_retries(logger=self.log):
            with attempt:
                serialize_errors = []
                self.log.debug(
                    "Running dagbag.sync_to_db with retries. Try %d of %d",
                    attempt.retry_state.attempt_number,
                    MAX_DB_RETRIES,
                )
                self.log.debug("Calling the DAG.bulk_sync_to_db method")
                try:
                    
                    for dag in self.dags.values():
                        serialize_errors.extend(_serialize_dag_capturing_errors(dag, session))
                    DAG.bulk_write_to_db(self.dags.values(), session=session)
                except OperationalError:
                    session.rollback()
                    raise
                
                
                self.import_errors.update(dict(serialize_errors))
    @provide_session
    def _sync_perm_for_dag(self, dag, session: Optional[Session] = None):