Avoid import of nose-based tests.utils, make skip_if_no_module() and skip_if_no_network() allowed at module level

[jwodder]

This PR addresses the test failures seen in the conda-forge feedstock:

• A remaining import of nose-based datalad.test.utils is updated so that nose is no longer needed during tests.
• Calling skip_if_no_module() and skip_if_no_network() at module level (as is done in datalad/downloaders/tests/test_s3.py) is now allowed.

I suggest releasing this in 0.17.1 soon so that a passing release can be made on conda-forge.

Changelog

🛡 Tests

• Fix failing tests on conda-forge

[yarikoptic]

I suggest releasing this in 0.17.1 soon so that a passing release can be made on conda-forge.

in general I would not oppose it but since diff is trivial and tests related, might be better to just take this diff as a patch for now. Meanwhile, adjusted the PR title to provide more details which would be taken into Changelog.

edit: I meanwhile will look into updating debian packaging, more gotchas might arise from it...

edit2: pushed as a patch in regro-cf-autotick-bot/datalad-feedstock@065e555

[codecov]

Codecov Report

Merging #6817 (0224e27) into maint (2dea515) will increase coverage by 0.95%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##            maint    #6817      +/-   ##
==========================================
+ Coverage   90.25%   91.20%   +0.95%     
==========================================
  Files         354      354              
  Lines       46057    46057              
==========================================
+ Hits        41567    42007     +440     
+ Misses       4490     4050     -440     

Impacted Files	Coverage Δ
datalad/runner/tests/test_threadsafety.py	100.00% <100.00%> (ø)
datalad/tests/utils_pytest.py	89.72% <100.00%> (ø)
datalad/tests/utils.py	66.76% <0.00%> (+9.55%)	⬆️
datalad/tests/test_tests_utils.py	92.34% <0.00%> (+92.34%)	⬆️

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[yarikoptic]

travis fail is the ssh copy one, known... unrelated. Let's proceed. thank you @jwodder . more fixes will pile up and then we will release. I think I accounted for all in conda feestock but may be there would be more

[github-actions]

🚀 PR was released in 0.17.1 🚀