[health] Adding DB check to /health (#4062)

superset/views/core.py

@@ -28,6 +28,7 @@ import pandas as pd
 import sqlalchemy as sqla
 from sqlalchemy import create_engine
 from sqlalchemy.engine.url import make_url
+from sqlalchemy.exc import OperationalError
 from unidecode import unidecode
 from werkzeug.routing import BaseConverter
 from werkzeug.utils import secure_filename
@@ -654,6 +655,11 @@ appbuilder.add_view(
 
 @app.route('/health')
 def health():
+    try:
+        db.session.execute('SELECT 1')
+    except OperationalError:
+        return Response('BAD', status=500)
+
     return 'OK'