[DATALAD RUNCMD] Make python 3.8 to be minimal python and test with it instead of EOLed 3.7

[yarikoptic]

hopefully makes benchmarking working great again

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 91.02%. Comparing base (c053aeb) to head (076c906).
Report is 10 commits behind head on master.

❗ Current head 076c906 differs from pull request most recent head 25e3ec7. Consider uploading reports for the commit 25e3ec7 to get more accurate results

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #108      +/-   ##
==========================================
+ Coverage   90.72%   91.02%   +0.29%     
==========================================
  Files          10       10              
  Lines         604      624      +20     
==========================================
+ Hits          548      568      +20     
  Misses         56       56              

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[yarikoptic]

apparently adding build didn't help. @jwodder - what can you find to have this addressed?

Run asv run --show-stderr --python 3.8 HEAD^-1
Couldn't load asv.plugins._mamba_helpers because
No module named 'libmambapy'

in a24e05f you committed

"Don't use asv 0.6.2"

without explanation -- why was that?

[yarikoptic]

ok - PR lead to airspeed-velocity/asv#1389 which is still open, but seems different from above fail

[jwodder]

@yarikoptic Is the purpose of this PR just to get benchmarking working, or do you actually want to drop 3.7 support separately from that?

[yarikoptic]

original idea was just on dropping 3.7 since EOLed but indeed then mixed in benchmarking... Let me drop commit for asv so we could just merge 3.7 drop separately and could you troubleshoot/fixup asv in a separate PR?

[jwodder]

@yarikoptic I tried to get asv working again following the hint the maintainer gave in that issue, but my best guess didn't work. I've posted again on the issue and am awaiting a response.