fix(hive): Fix regression from #21943

[john-bodley]

SUMMARY

This PR fixes a regression introduced in #21943 where no context manger was used to create the engine, thus preventing users from being able to upload a CSV file via Hive.

I thought both Pylint would have detected a "Local variable referenced before assignment" error, but maybe the if/context manager logic was simply too complex, as well as the unit tests—but alas this doesn't seem to be the case.

BEFORE/AFTER SCREENSHOTS OR ANIMATED GIF

TESTING INSTRUCTIONS

Tested locally.

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

[john-bodley]

This line is new. The rest is merely indented.

[codecov]

Codecov Report

Merging #22431 (f7afd8b) into master (fa919f3) will decrease coverage by 11.35%.
The diff coverage is 0.00%.

@@             Coverage Diff             @@
##           master   #22431       +/-   ##
===========================================
- Coverage   66.90%   55.54%   -11.36%     
===========================================
  Files        1850     1850               
  Lines       70692    70693        +1     
  Branches     7752     7752               
===========================================
- Hits        47294    39269     -8025     
- Misses      21382    29408     +8026     
  Partials     2016     2016               

Flag	Coverage Δ
hive	?
mysql	?
postgres	?
presto	52.36% <0.00%> (-0.01%)	⬇️
python	57.40% <0.00%> (-23.84%)	⬇️
sqlite	?
unit	50.92% <0.00%> (-0.01%)	⬇️

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

Impacted Files	Coverage Δ
superset/db_engine_specs/hive.py	34.25% <0.00%> (-53.10%)	⬇️
superset/utils/dashboard_import_export.py	0.00% <0.00%> (-100.00%)	⬇️
superset/tags/core.py	4.54% <0.00%> (-95.46%)	⬇️
superset/key_value/commands/update.py	0.00% <0.00%> (-90.91%)	⬇️
superset/key_value/commands/delete.py	0.00% <0.00%> (-87.88%)	⬇️
superset/db_engines/hive.py	0.00% <0.00%> (-85.19%)	⬇️
superset/key_value/commands/delete_expired.py	0.00% <0.00%> (-84.00%)	⬇️
superset/dashboards/commands/importers/v0.py	15.62% <0.00%> (-76.25%)	⬇️
superset/datasets/commands/create.py	30.61% <0.00%> (-69.39%)	⬇️
superset/datasets/commands/update.py	25.00% <0.00%> (-69.05%)	⬇️
... and 284 more

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[villebro]

@john-bodley I've run into several problems with mypy lately where it's not picking up trivial typing errors. I wasn't able to look into it more closely, but I did try bumping mypy locally and even enabling all checks, but it still kept glossing over the errors.