Triggering a dagrun with naive datetime raises an HTML page instead of JSON

**Apache Airflow version**:2.0


**What happened**:

An HTML page was returned instead of json when the REST API was triggered with a naive datetime

**What you expected to happen**:

I expected it to raise error status 400 indicating that it's a bad request

**How to reproduce it**:
1. Start the web server and scheduler inside breeze.
2. Make a post request to this endpoint: http://localhost:28080/api/v1/dags/example_bash_operator/dagRuns
 to trigger dagruns using this request body: {"execution_date": "2020-11-09T16:25:56.939143"}. or any naive datetime
3. See that an HTML is raised instead of Json

airflow/api_connexion/endpoints/dag_run_endpoint.py
query, end_date_gte, end_date_lte, execution_date_gte, execution_date_lte, start_date_gte, start_date_lte
):
    
    if start_date_gte:
        query = query.filter(DagRun.start_date >= start_date_gte)
    if start_date_lte:
        query = query.filter(DagRun.start_date <= start_date_lte)
    
    if execution_date_gte:
        query = query.filter(DagRun.execution_date >= execution_date_gte)
    if execution_date_lte:
        query = query.filter(DagRun.execution_date <= execution_date_lte)
    
    if end_date_gte:
        query = query.filter(DagRun.end_date >= end_date_gte)
    if end_date_lte:
        query = query.filter(DagRun.end_date <= end_date_lte)
    return query
@security.requires_access(
    [
        (permissions.ACTION_CAN_READ, permissions.RESOURCE_DAG),
        (permissions.ACTION_CAN_READ, permissions.RESOURCE_DAG_RUN),
    ]
)
@provide_session
def get_dag_runs_batch(session):