Add rimport tests

[samsrabin]

Required a tiny code change to rimport in order for its system tests to work, since authentication is impossible during pytest.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 98.54545% with 8 lines in your changes missing coverage. Please review.
⚠️ Please upload report for BASE (main@db095fd). Learn more about missing BASE report.

Files with missing lines	Patch %	Lines
rimport	0.00%	2 Missing ⚠️
tests/rimport/test_build_parser.py	98.59%	1 Missing ⚠️
tests/rimport/test_ensure_running_as.py	98.48%	1 Missing ⚠️
tests/rimport/test_get_staging_root.py	98.33%	1 Missing ⚠️
tests/rimport/test_read_filelist.py	98.70%	1 Missing ⚠️
tests/rimport/test_resolve_paths.py	98.71%	1 Missing ⚠️
tests/rimport/test_stage_data.py	98.90%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #16   +/-   ##
=======================================
  Coverage        ?   97.55%           
=======================================
  Files           ?       20           
  Lines           ?     2005           
  Branches        ?        0           
=======================================
  Hits            ?     1956           
  Misses          ?       49           
  Partials        ?        0           

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