Local weather-mv runs not working

Local `weather-mv` runs for both `bq` and `rg` are failing with `AttributeError` exceptions, when following `weather_mv`'s README instructions. The same commands seem to be working in Dataflow (with the correct runner image, in case of `rg`). In the case of `weather-mv bq`, the failure happens quite late in the execution.

## `weather-mv bq`

**command**
```bash
weather-mv bigquery --uris "gs://$BUCKET/download/*.nc" --output_table $PROJECT.$DATASET_ID.$TABLE_ID --temp_location "gs://$BUCKET/tmp" --direct_num_workers=4
```

**error**
```raw
Traceback (most recent call last):
File "/venv38/bin/weather-mv", line 74, in
cli(['--extra_package', pkg_archive])
File "/venv38/lib/python3.8/site-packages/weather_mv/loader_pipeline/__init__.py", line 23, in cli
pipeline(*run(sys.argv + extra))
File "/venv38/lib/python3.8/site-packages/weather_mv/loader_pipeline/pipeline.py", line 157, in pipeline
paths | "MoveToBigQuery" >> ToBigQuery.from_kwargs(example_uri=next(iter(all_uris)), **vars(known_args))
File "/venv38/lib/python3.8/site-packages/apache_beam/pipeline.py", line 597, in __exit__
self.result = self.run()
File "/venv38/lib/python3.8/site-packages/apache_beam/pipeline.py", line 574, in run
return self.runner.run_pipeline(self, self._options)
File "/venv38/lib/python3.8/site-packages/apache_beam/runners/direct/direct_runner.py", line 131, in run_pipeline
return runner.run_pipeline(pipeline, options)
File "/venv38/lib/python3.8/site-packages/apache_beam/runners/portability/fn_api_runner/fn_runner.py", line 199, in run_pipeline
self._latest_run_result = self.run_via_runner_api(
File "/venv38/lib/python3.8/site-packages/apache_beam/runners/portability/fn_api_runner/fn_runner.py", line 212, in run_via_runner_api
return self.run_stages(stage_context, stages)
File "/venv38/lib/python3.8/site-packages/apache_beam/runners/portability/fn_api_runner/fn_runner.py", line 442, in run_stages
bundle_results = self._execute_bundle(
File "/venv38/lib/python3.8/site-packages/apache_beam/runners/portability/fn_api_runner/fn_runner.py", line 770, in _execute_bundle
self._run_bundle(
File "/venv38/lib/python3.8/site-packages/apache_beam/runners/portability/fn_api_runner/fn_runner.py", line 999, in _run_bundle
result, splits = bundle_manager.process_bundle(
File "/venv38/lib/python3.8/site-packages/apache_beam/runners/portability/fn_api_runner/fn_runner.py", line 1393, in process_bundle
for ix, part in enumerate(input.partition(self._num_workers)):
AttributeError: 'NoneType' object has no attribute 'partition'
```

## `weather-mv rg`

**command**
```bash
./weather_mv/weather-mv regrid --uris "gs://$BUCKET/download/*.nc" --output_path="gs://$BUCKET/download-002-rg-$(date +%s)/" --direct_num_workers=4
```

**error**
```raw

Traceback (most recent call last):
File "apache_beam/runners/common.py", line 1417, in apache_beam.runners.common.DoFnRunner.process
File "apache_beam/runners/common.py", line 624, in apache_beam.runners.common.SimpleInvoker.invoke_process
File "/python3.8/site-packages/apache_beam/transforms/core.py", line 1845, in
wrapper = lambda x: [fn(x)]
File "/weather_mv/loader_pipeline/regrid.py", line 86, in apply
fs = mv.bindings.Fieldset(path=local_grib)
AttributeError: 'NoneType' object has no attribute 'bindings'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
File "./weather_mv/weather-mv", line 74, in
cli(['--extra_package', pkg_archive])
File "/weather_mv/loader_pipeline/__init__.py", line 23, in cli
pipeline(*run(sys.argv + extra))
File "/weather_mv/loader_pipeline/pipeline.py", line 69, in pipeline
raise ValueError('invalid subcommand!')
File "/python3.8/site-packages/apache_beam/pipeline.py", line 597, in __exit__
self.result = self.run()
File "/python3.8/site-packages/apache_beam/pipeline.py", line 574, in run
return self.runner.run_pipeline(self, self._options)
File "/python3.8/site-packages/apache_beam/runners/direct/direct_runner.py", line 131, in run_pipeline
return runner.run_pipeline(pipeline, options)
File "/python3.8/site-packages/apache_beam/runners/portability/fn_api_runner/fn_runner.py", line 199, in run_pipeline
self._latest_run_result = self.run_via_runner_api(
File "/python3.8/site-packages/apache_beam/runners/portability/fn_api_runner/fn_runner.py", line 212, in run_via_runner_api
return self.run_stages(stage_context, stages)
File "/python3.8/site-packages/apache_beam/runners/portability/fn_api_runner/fn_runner.py", line 442, in run_stages
bundle_results = self._execute_bundle(
File "/python3.8/site-packages/apache_beam/runners/portability/fn_api_runner/fn_runner.py", line 770, in _execute_bundle
self._run_bundle(
File "/python3.8/site-packages/apache_beam/runners/portability/fn_api_runner/fn_runner.py", line 999, in _run_bundle
result, splits = bundle_manager.process_bundle(
File "/python3.8/site-packages/apache_beam/runners/portability/fn_api_runner/fn_runner.py", line 1415, in process_bundle
for result, split_result in executor.map(execute, zip(part_inputs, # pylint: disable=bad-option-value
File "/python3.8/concurrent/futures/_base.py", line 619, in result_iterator
yield fs.pop().result()
File "/python3.8/concurrent/futures/_base.py", line 444, in result
return self.__get_result()
File "/python3.8/concurrent/futures/_base.py", line 389, in __get_result
raise self._exception
File "/python3.8/site-packages/apache_beam/utils/thread_pool_executor.py", line 37, in run
self._future.set_result(self._fn(*self._fn_args, **self._fn_kwargs))
File "/python3.8/site-packages/apache_beam/runners/portability/fn_api_runner/fn_runner.py", line 1407, in execute
return bundle_manager.process_bundle(
File "/python3.8/site-packages/apache_beam/runners/portability/fn_api_runner/fn_runner.py", line 1309, in process_bundle
result_future = self._worker_handler.control_conn.push(process_bundle_req)
File "/python3.8/site-packages/apache_beam/runners/portability/fn_api_runner/worker_handlers.py", line 379, in push
response = self.worker.do_instruction(request)
File "/python3.8/site-packages/apache_beam/runners/worker/sdk_worker.py", line 597, in do_instruction
return getattr(self, request_type)(
File "/python3.8/site-packages/apache_beam/runners/worker/sdk_worker.py", line 635, in process_bundle
bundle_processor.process_bundle(instruction_id))
File "/python3.8/site-packages/apache_beam/runners/worker/bundle_processor.py", line 1003, in process_bundle
input_op_by_transform_id[element.transform_id].process_encoded(
File "/python3.8/site-packages/apache_beam/runners/worker/bundle_processor.py", line 227, in process_encoded
self.output(decoded_value)
File "apache_beam/runners/worker/operations.py", line 526, in apache_beam.runners.worker.operations.Operation.output
File "apache_beam/runners/worker/operations.py", line 528, in apache_beam.runners.worker.operations.Operation.output
File "apache_beam/runners/worker/operations.py", line 237, in apache_beam.runners.worker.operations.SingletonElementConsumerSet.receive
File "apache_beam/runners/worker/operations.py", line 240, in apache_beam.runners.worker.operations.SingletonElementConsumerSet.receive
File "apache_beam/runners/worker/operations.py", line 907, in apache_beam.runners.worker.operations.DoOperation.process
File "apache_beam/runners/worker/operations.py", line 908, in apache_beam.runners.worker.operations.DoOperation.process
File "apache_beam/runners/common.py", line 1419, in apache_beam.runners.common.DoFnRunner.process
File "apache_beam/runners/common.py", line 1491, in apache_beam.runners.common.DoFnRunner._reraise_augmented
File "apache_beam/runners/common.py", line 1417, in apache_beam.runners.common.DoFnRunner.process
File "apache_beam/runners/common.py", line 623, in apache_beam.runners.common.SimpleInvoker.invoke_process
File "apache_beam/runners/common.py", line 1581, in apache_beam.runners.common._OutputHandler.handle_process_outputs
File "apache_beam/runners/common.py", line 1694, in apache_beam.runners.common._OutputHandler._write_value_to_tag
File "apache_beam/runners/worker/operations.py", line 240, in apache_beam.runners.worker.operations.SingletonElementConsumerSet.receive
File "apache_beam/runners/worker/operations.py", line 907, in apache_beam.runners.worker.operations.DoOperation.process
File "apache_beam/runners/worker/operations.py", line 908, in apache_beam.runners.worker.operations.DoOperation.process
File "apache_beam/runners/common.py", line 1419, in apache_beam.runners.common.DoFnRunner.process
File "apache_beam/runners/common.py", line 1491, in apache_beam.runners.common.DoFnRunner._reraise_augmented
File "apache_beam/runners/common.py", line 1417, in apache_beam.runners.common.DoFnRunner.process
File "apache_beam/runners/common.py", line 623, in apache_beam.runners.common.SimpleInvoker.invoke_process
File "apache_beam/runners/common.py", line 1581, in apache_beam.runners.common._OutputHandler.handle_process_outputs
File "apache_beam/runners/common.py", line 1694, in apache_beam.runners.common._OutputHandler._write_value_to_tag
File "apache_beam/runners/worker/operations.py", line 240, in apache_beam.runners.worker.operations.SingletonElementConsumerSet.receive
File "apache_beam/runners/worker/operations.py", line 907, in apache_beam.runners.worker.operations.DoOperation.process
File "apache_beam/runners/worker/operations.py", line 908, in apache_beam.runners.worker.operations.DoOperation.process
File "apache_beam/runners/common.py", line 1419, in apache_beam.runners.common.DoFnRunner.process
File "apache_beam/runners/common.py", line 1491, in apache_beam.runners.common.DoFnRunner._reraise_augmented
File "apache_beam/runners/common.py", line 1417, in apache_beam.runners.common.DoFnRunner.process
File "apache_beam/runners/common.py", line 623, in apache_beam.runners.common.SimpleInvoker.invoke_process
File "apache_beam/runners/common.py", line 1581, in apache_beam.runners.common._OutputHandler.handle_process_outputs
File "apache_beam/runners/common.py", line 1694, in apache_beam.runners.common._OutputHandler._write_value_to_tag
File "apache_beam/runners/worker/operations.py", line 240, in apache_beam.runners.worker.operations.SingletonElementConsumerSet.receive
File "apache_beam/runners/worker/operations.py", line 907, in apache_beam.runners.worker.operations.DoOperation.process
File "apache_beam/runners/worker/operations.py", line 908, in apache_beam.runners.worker.operations.DoOperation.process
File "apache_beam/runners/common.py", line 1419, in apache_beam.runners.common.DoFnRunner.process
File "apache_beam/runners/common.py", line 1507, in apache_beam.runners.common.DoFnRunner._reraise_augmented
File "apache_beam/runners/common.py", line 1417, in apache_beam.runners.common.DoFnRunner.process
File "apache_beam/runners/common.py", line 624, in apache_beam.runners.common.SimpleInvoker.invoke_process
File "/python3.8/site-packages/apache_beam/transforms/core.py", line 1845, in
wrapper = lambda x: [fn(x)]
File "/weather_mv/loader_pipeline/regrid.py", line 86, in apply
fs = mv.bindings.Fieldset(path=local_grib)
AttributeError: 'NoneType' object has no attribute 'bindings' [while running 'Regrid/Map(apply)']

```