Use triple-quoted string

Author: tjkuson

pytest_asyncio/plugin.py

@@ -236,10 +236,10 @@ def _get_asyncio_debug(config: Config) -> bool:
         return val == "true"
 
 
-_INVALID_LOOP_FACTORIES = (
-    "pytest_asyncio_loop_factories must return a non-empty mapping of factory names "
-    "to callables."
-)
+_INVALID_LOOP_FACTORIES = """\
+pytest_asyncio_loop_factories must return a non-empty mapping of \
+factory names to callables.
+"""
 
 
 def _collect_hook_loop_factories(