Fix isort lint (#1183)

Author: basepi

tests/contrib/asyncio/starlette_tests.py

@@ -28,13 +28,14 @@
 #  OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 #  OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
-import os
 import pytest  # isort:skip
 
 from tests.fixtures import TempStoreClient
 
 starlette = pytest.importorskip("starlette")  # isort:skip
 
+import os
+
 import mock
 import urllib3
 from starlette.applications import Starlette