fix: adding encoding. It is required by S3Boto3Storage.

[awais786]

Upgrade PR from boto to boto3 gives error on production.

Run this command python manage.py cms export_course_metadata_for_all_courses.

Faced errors on edxapp-cms-worker related to Course Metadata failure with following stack trace

[2023-02-09 13:29:44,028: ERROR/ForkPoolWorker-15] Task cms.djangoapps.export_course_metadata.tasks.export_course_metadata_task[1978fb43-09a0-4973-9cd4-8635aca89aec] raised unexpected: TypeError('Unicode-objects must be encoded before hashing')
Traceback (most recent call last):
  File "/edx/app/edxapp/venvs/edxapp/lib/python3.8/site-packages/celery/app/trace.py", line 451, in trace_task
    R = retval = fun(*args, **kwargs)
  File "/edx/app/edxapp/venvs/edxapp/lib/python3.8/site-packages/newrelic/hooks/application_celery.py", line 99, in wrapper
    return wrapped(*args, **kwargs)
  File "/edx/app/edxapp/venvs/edxapp/lib/python3.8/site-packages/celery/app/trace.py", line 734, in __protected_call__
    return self.run(*args, **kwargs)
  File "/edx/app/edxapp/edx-platform/cms/djangoapps/export_course_metadata/tasks.py", line 31, in export_course_metadata_task
    course_metadata_export_storage.save(f'course_metadata_export/{course_key}.json', highlights_content)
  File "/edx/app/edxapp/venvs/edxapp/lib/python3.8/site-packages/django/core/files/storage.py", line 54, in save
    name = self._save(name, content)
  File "/edx/app/edxapp/venvs/edxapp/lib/python3.8/site-packages/storages/backends/s3boto3.py", line 495, in _save
    self._save_content(obj, content, parameters=parameters)
  File "/edx/app/edxapp/venvs/edxapp/lib/python3.8/site-packages/storages/backends/s3boto3.py", line 510, in _save_content
    obj.upload_fileobj(content, ExtraArgs=put_parameters)
  File "/edx/app/edxapp/venvs/edxapp/lib/python3.8/site-packages/boto3/s3/inject.py", line 511, in object_upload_fileobj
    return self.meta.client.upload_fileobj(
  File "/edx/app/edxapp/venvs/edxapp/lib/python3.8/site-packages/boto3/s3/inject.py", line 431, in upload_fileobj
    return future.result()
  File "/edx/app/edxapp/venvs/edxapp/lib/python3.8/site-packages/s3transfer/futures.py", line 73, in result
    return self._coordinator.result()
  File "/edx/app/edxapp/venvs/edxapp/lib/python3.8/site-packages/s3transfer/futures.py", line 233, in result
    raise self._exception
  File "/edx/app/edxapp/venvs/edxapp/lib/python3.8/site-packages/s3transfer/tasks.py", line 126, in __call__
    return self._execute_main(kwargs)
  File "/edx/app/edxapp/venvs/edxapp/lib/python3.8/site-packages/s3transfer/tasks.py", line 150, in _execute_main
    return_value = self._main(**kwargs)
  File "/edx/app/edxapp/venvs/edxapp/lib/python3.8/site-packages/s3transfer/upload.py", line 692, in _main
    client.put_object(Bucket=bucket, Key=key, Body=body, **extra_args)
  File "/edx/app/edxapp/venvs/edxapp/lib/python3.8/site-packages/botocore/client.py", line 317, in _api_call
    return self._make_api_call(operation_name, kwargs)
  File "/edx/app/edxapp/venvs/edxapp/lib/python3.8/site-packages/botocore/client.py", line 591, in _make_api_call
    handler, event_response = self.meta.events.emit_until_response(
  File "/edx/app/edxapp/venvs/edxapp/lib/python3.8/site-packages/botocore/hooks.py", line 242, in emit_until_response
    responses = self._emit(event_name, kwargs, stop_on_response=True)
  File "/edx/app/edxapp/venvs/edxapp/lib/python3.8/site-packages/botocore/hooks.py", line 210, in _emit
    response = handler(**kwargs)
  File "/edx/app/edxapp/venvs/edxapp/lib/python3.8/site-packages/botocore/handlers.py", line 209, in conditionally_calculate_md5
    calculate_md5(params, **kwargs)
  File "/edx/app/edxapp/venvs/edxapp/lib/python3.8/site-packages/botocore/handlers.py", line 187, in calculate_md5
    binary_md5 = _calculate_md5_from_file(body)
  File "/edx/app/edxapp/venvs/edxapp/lib/python3.8/site-packages/botocore/handlers.py", line 201, in _calculate_md5_from_file
    md5.update(chunk)
TypeError: Unicode-objects must be encoded before hashing

Boto3 PR #31282

We are testing this change on boto.

[awais786]

down the stream it tried to encoded here also. So eventually encoding is happening

[iamsobanjaved]

I verified that json.loads works fine with encoded value.