[sdk/python] Avoid 'referenced before assignment' error
We have seen cases where a lot of errors like this are reported:
```
UnboundLocalError: local variable 'resources' referenced before assignment
```
This change prevents this failure mode, which might be a symptom of some
other issue, but currently obscures it in the error path.
@@ -152,6 +152,7 @@ class Output(Generic[T_co]):
# The "run" coroutine actually runs the apply.
async def run() -> U:
+ resources: Set['Resource'] = set()
try:
# Await this output's details.
resources = await self._resources
