chore: use os.getenv to simplify superset_config.py

[sebastianliebscher]

SUMMARY

This PR removes a function in superset_config.py and replaces it by built-in os.getenv(). Instead of raising an exception when the env variable is missing, they now have a default value. Their default values are the same as in .env file (same values as in .env-non-dev)

TESTING INSTRUCTIONS

Changes in superset_config.py only affect docker deployments, so in order to test this PR run docker-compose up and check variables values.

ADDITIONAL INFORMATION

• Has associated issue:
• Required feature flags:
• Changes UI
• Includes DB Migration (follow approval process in SIP-59)
  • Migration is atomic, supports rollback & is backwards-compatible
  • Confirm DB migration upgrade and downgrade tested
  • Runtime estimates and downtime expectations provided
• Introduces new feature or API
• Removes existing feature or API

[sebastianliebscher]

Python Misc / pre-commit is failing with

mypy.....................................................................Failed
- hook id: mypy
- exit code: 1

docker/pythonpath_dev/superset_config.py:38: error: Name "get_env_variable" is not defined  [name-defined]
docker/pythonpath_dev/superset_config.py:39: error: Name "get_env_variable" is not defined  [name-defined]
docker/pythonpath_dev/superset_config.py:40: error: Name "get_env_variable" is not defined  [name-defined]
docker/pythonpath_dev/superset_config.py:41: error: Name "get_env_variable" is not defined  [name-defined]
docker/pythonpath_dev/superset_config.py:42: error: Name "get_env_variable" is not defined  [name-defined]

This is the function I removed with this PR. Locally, all pre-commit checks run successfully.

[sebastianliebscher]

Ah, OK. There are new variables from a new commit in master.

[john-bodley]

@sebastianliebscher would you mind describing where the defaults are coming from via either updating your PR description or adding inline review comments?

[michael-s-molina]

LGTM

[john-bodley]

@sebastianliebscher I'm a tad confused. You linked to the .env-non-dev file which would indicate that now we have two places (as opposed to one) where the same defaults are defined and thus this doesn't seem to adhere to the DRY principle.

[sebastianliebscher]

Since I have only now come to it: For completeness @john-bodley's concerns were resolved in #25055.