Fix coverage

Author: Cito

src/graphql/execution/map_async_iterator.py

@@ -84,7 +84,7 @@ async def athrow(
             await self.aclose()
             if value is None:
                 if traceback is None:
-                    raise type_
+                    raise type_  # pragma: no cover
                 value = (
                     type_
                     if isinstance(value, BaseException)

src/graphql/pyutils/description.py

@@ -44,7 +44,7 @@ def unregister(cls, base: type) -> None:
         if not isinstance(base, type):
             raise TypeError("Only types can be unregistered.")
         if isinstance(cls.bases, tuple):
-            if base in cls.bases:
+            if base in cls.bases:  # pragma: no branch
                 cls.bases = tuple(b for b in cls.bases if b is not base)
             if not cls.bases:
                 cls.bases = object

tests/execution/test_executor.py

@@ -572,11 +572,7 @@ def handles_sync_errors_combined_with_async_ones():
 
         async def async_resolver(_obj, _info):
             nonlocal is_async_resolver_finished
-            sleep = asyncio.sleep
-            sleep(0)
-            sleep(0)
-            sleep(0)
-            is_async_resolver_finished = True
+            is_async_resolver_finished = True  # pragma: no cover
 
         schema = GraphQLSchema(
             GraphQLObjectType(