fix: import superset_config

[villebro]

SUMMARY

A recent PR #15405 replaced the use of the deprecated imp.load_source with importlib.load_module, which caused the following error on some deployments:

Failed to import config for SUPERSET_CONFIG_PATH=/Users/ville/superset/superset_config.py
Traceback (most recent call last):
  File "/Users/ville/src/superset/superset/app.py", line 80, in load_override_config
    override_conf = importlib.import_module("superset_config", cfg_path)
  File "/Users/ville/.pyenv/versions/3.8-dev/lib/python3.8/importlib/__init__.py", line 127, in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
  File "<frozen importlib._bootstrap>", line 1014, in _gcd_import
  File "<frozen importlib._bootstrap>", line 991, in _find_and_load
  File "<frozen importlib._bootstrap>", line 973, in _find_and_load_unlocked
ModuleNotFoundError: No module named 'superset_config'
Failed to create app
Traceback (most recent call last):
  File "/Users/ville/src/superset/superset/app.py", line 40, in create_app
    config = init_config()
  File "/Users/ville/src/superset/superset/app.py", line 56, in init_config
    override_conf = convert_to_dict(load_override_config())
  File "/Users/ville/src/superset/superset/app.py", line 80, in load_override_config
    override_conf = importlib.import_module("superset_config", cfg_path)
  File "/Users/ville/.pyenv/versions/3.8-dev/lib/python3.8/importlib/__init__.py", line 127, in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
  File "<frozen importlib._bootstrap>", line 1014, in _gcd_import
  File "<frozen importlib._bootstrap>", line 991, in _find_and_load
  File "<frozen importlib._bootstrap>", line 973, in _find_and_load_unlocked
ModuleNotFoundError: No module named 'superset_config'
Traceback (most recent call last):
  File "/Users/ville/src/superset/venv/bin/superset", line 11, in <module>
    load_entry_point('apache-superset', 'console_scripts', 'superset')()
  File "/Users/ville/src/superset/venv/lib/python3.8/site-packages/click/core.py", line 829, in __call__
    return self.main(*args, **kwargs)
  File "/Users/ville/src/superset/venv/lib/python3.8/site-packages/flask/cli.py", line 586, in main
    return super(FlaskGroup, self).main(*args, **kwargs)
  File "/Users/ville/src/superset/venv/lib/python3.8/site-packages/click/core.py", line 782, in main
    rv = self.invoke(ctx)
  File "/Users/ville/src/superset/venv/lib/python3.8/site-packages/click/core.py", line 1256, in invoke
    Command.invoke(self, ctx)
  File "/Users/ville/src/superset/venv/lib/python3.8/site-packages/click/core.py", line 1066, in invoke
    return ctx.invoke(self.callback, **ctx.params)
  File "/Users/ville/src/superset/venv/lib/python3.8/site-packages/click/core.py", line 610, in invoke
    return callback(*args, **kwargs)
  File "/Users/ville/src/superset/venv/lib/python3.8/site-packages/click/decorators.py", line 21, in new_func
    return f(get_current_context(), *args, **kwargs)
  File "/Users/ville/src/superset/venv/lib/python3.8/site-packages/flask/cli.py", line 425, in decorator
    with __ctx.ensure_object(ScriptInfo).load_app().app_context():
  File "/Users/ville/src/superset/venv/lib/python3.8/site-packages/flask/cli.py", line 381, in load_app
    app = call_factory(self, self.create_app)
  File "/Users/ville/src/superset/venv/lib/python3.8/site-packages/flask/cli.py", line 119, in call_factory
    return app_factory()
  File "/Users/ville/src/superset/superset/app.py", line 51, in create_app
    raise ex
  File "/Users/ville/src/superset/superset/app.py", line 40, in create_app
    config = init_config()
  File "/Users/ville/src/superset/superset/app.py", line 56, in init_config
    override_conf = convert_to_dict(load_override_config())
  File "/Users/ville/src/superset/superset/app.py", line 80, in load_override_config
    override_conf = importlib.import_module("superset_config", cfg_path)
  File "/Users/ville/.pyenv/versions/3.8-dev/lib/python3.8/importlib/__init__.py", line 127, in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
  File "<frozen importlib._bootstrap>", line 1014, in _gcd_import
  File "<frozen importlib._bootstrap>", line 991, in _find_and_load
  File "<frozen importlib._bootstrap>", line 973, in _find_and_load_unlocked
ModuleNotFoundError: No module named 'superset_config'

A similar change was done on Airflow last year: apache/airflow#7099 , which is based on the official documentation found here: https://docs.python.org/3/library/importlib.html#importing-a-source-file-directly.

BEFORE/AFTER SCREENSHOTS OR ANIMATED GIF

TESTING INSTRUCTIONS

ADDITIONAL INFORMATION

• Has associated issue:
• 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

[zhaoyongjie]

LGTM

[codecov]

Codecov Report

Merging #15444 (ccad28a) into master (ed6d10e) will decrease coverage by 0.23%.
The diff coverage is 25.00%.

@@            Coverage Diff             @@
##           master   #15444      +/-   ##
==========================================
- Coverage   77.21%   76.98%   -0.24%     
==========================================
  Files         975      975              
  Lines       50662    50668       +6     
  Branches     6228     6228              
==========================================
- Hits        39120    39005     -115     
- Misses      11331    11452     +121     
  Partials      211      211              

Flag	Coverage Δ
hive	?
mysql	81.71% <25.00%> (-0.02%)	⬇️
postgres	81.73% <25.00%> (-0.02%)	⬇️
presto	?
python	81.82% <25.00%> (-0.46%)	⬇️
sqlite	81.35% <25.00%> (-0.02%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
superset/app.py	63.49% <25.00%> (-4.93%)	⬇️
superset/db_engines/hive.py	0.00% <0.00%> (-82.15%)	⬇️
superset/db_engine_specs/hive.py	69.20% <0.00%> (-17.21%)	⬇️
superset/db_engine_specs/presto.py	83.36% <0.00%> (-6.53%)	⬇️
superset/views/database/mixins.py	81.03% <0.00%> (-1.73%)	⬇️
superset/connectors/sqla/models.py	88.22% <0.00%> (-1.65%)	⬇️
superset/db_engine_specs/base.py	87.97% <0.00%> (-0.41%)	⬇️
superset/models/core.py	89.76% <0.00%> (-0.27%)	⬇️
superset/utils/core.py	88.97% <0.00%> (-0.13%)	⬇️

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