[pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

src/cloudevents/core/v1/exceptions.py

@@ -32,7 +32,8 @@ class CloudEventValidationError(BaseCloudEventException):
 
     def __str__(self) -> str:
         error_messages = [
-            f"{key}: {', '.join(str(e) for e in value)}" for key, value in self.errors.items()
+            f"{key}: {', '.join(str(e) for e in value)}"
+            for key, value in self.errors.items()
         ]
         return f"{super().__str__()}: {', '.join(error_messages)}"