WIP: testing python-based impersonation

[kennknowles]

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[kennknowles]

Locally ./gradlew :sdks:python:test-suites:dataflow:py38:postCommitIT passed, so checking it is not a false signal since #17244 was not passing. I'll leave this here. I think there are refactors in that PR that I have not got integrated to this branch.

[kennknowles]

Run Python 3.8 PostCommit

[codecov]

Codecov Report

Merging #17644 (caa3662) into master (f30e4e5) will decrease coverage by 0.00%.
The diff coverage is 70.00%.

@@            Coverage Diff             @@
##           master   #17644      +/-   ##
==========================================
- Coverage   73.95%   73.94%   -0.01%     
==========================================
  Files         693      693              
  Lines       91720    91745      +25     
==========================================
+ Hits        67832    67845      +13     
- Misses      22639    22651      +12     
  Partials     1249     1249              

Flag	Coverage Δ
python	83.70% <70.00%> (-0.02%)	⬇️

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

Impacted Files	Coverage Δ
sdks/python/apache_beam/io/gcp/bigquery_tools.py	83.15% <ø> (ø)
...ks/python/apache_beam/runners/interactive/utils.py	95.06% <ø> (ø)
..._beam/runners/portability/sdk_container_builder.py	37.93% <0.00%> (ø)
...apache_beam/runners/dataflow/internal/apiclient.py	77.39% <50.00%> (+0.03%)	⬆️
sdks/python/apache_beam/internal/gcp/auth.py	73.33% <61.53%> (-7.71%)	⬇️
sdks/python/apache_beam/io/gcp/gcsfilesystem.py	88.65% <82.35%> (+0.41%)	⬆️
sdks/python/apache_beam/io/gcp/gcsio.py	92.26% <100.00%> (ø)
...dks/python/apache_beam/options/pipeline_options.py	94.93% <100.00%> (+0.01%)	⬆️
.../python/apache_beam/testing/test_stream_service.py	88.09% <0.00%> (-4.77%)	⬇️
...ache_beam/runners/dataflow/test_dataflow_runner.py	29.62% <0.00%> (-3.03%)	⬇️
... and 8 more

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[tvalentyn]

Run Python 3.8 PostCommit

[kennknowles]

Interesting that it passed

[kennknowles]

oh yea, we determined that it was because the tests were interacting via global state, so when i narrow it to just this test it passes