Attempt to fix Opensuse Leap 15.6 nightlies

This has been failing because it uses Python 3.6.  Until we have figured
out when we can roll platform off (#11679), let's try to fix this.  Untested.

tests/test_driver.py

@@ -193,7 +193,7 @@ async def main():
 
         semaphore = asyncio.Semaphore(max_concurrency) if max_concurrency else None
 
-        async def run(f, arg):
+        async def run(f, arg) -> TestResult:
             # TODO(python>3.8): use "async with"
             if semaphore is not None:
                 await semaphore.acquire()
@@ -205,7 +205,7 @@ async def main():
                 if semaphore is not None:
                     semaphore.release()
 
-        tasks = [asyncio.create_task(run(f, arg), name=arg) for f, arg in files]
+        tasks = [create_task(run(f, arg), name=arg) for f, arg in files]
         while tasks:
             done, tasks = await asyncio.wait(tasks, return_when=asyncio.FIRST_COMPLETED)
             for task in done:
@@ -276,6 +276,14 @@ class TestPass:
 TestResult = Union[TestSkip, TestFail, TestPass]
 
 
+# TODO(python>3.8): use asyncio.create_task
+def create_task(coro, name: str) -> asyncio.Task:
+    task = asyncio.Task(coro)
+    if sys.version_info >= (3, 8):
+        task.set_name(name)
+    return task
+
+
 async def run_test(
     tmp_root: Path,
     test_file_path: str,