[tox] Allowing running of specific tests (#9097)

tests/database_api_tests.py

@@ -14,11 +14,13 @@
 # KIND, either express or implied.  See the License for the
 # specific language governing permissions and limitations
 # under the License.
+# isort:skip_file
 """Unit tests for Superset"""
 import json
 
 import prison
 
+import tests.test_app
 from superset import db
 from superset.models.core import Database
 from superset.utils.core import get_example_database