WHY
The following readers/writers are using implicit config.<VAR> variables:

• gcs_reader, via the object_storage_reader
  • config.PROJECT_ID
• s3_reader, via the object_storage_reader
  • config.REGION_NAME, config.AWS_ACCESS_KEY_ID, config.AWS_SECRET_ACCESS_KEY
• gcs_writer
  • config.PROJECT_ID
• bq_writer
  • config.PROJECT_ID

These variables are not provided by the user as click options, but as environment variables. These environment variables are retrieved from the following snippet that appears in the nck/config.py module:

for key, var in os.environ.items():
    locals()[key] = var

This can be quite confusing for the user, and does not match the common NCK logic.

HOW
Explicitly implement these variables as click options