[CI][Python] Failing conda-python-3.9 Nightly Build

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The build segfaults after running the Python tests.
Very similar to https://issues.apache.org/jira/browse/ARROW-11146

Reporter: Mauricio 'Pachá' Vargas Sepúlveda / @pachadotdev
Assignee: Joris Van den Bossche / @jorisvandenbossche

PRs and other links:

• GitHub Pull Request #10185

_{Note: This issue was originally created as ARROW-12543. Please see the migration documentation for further details.}

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Joris Van den Bossche / @jorisvandenbossche:
It doesn't seem it's segfaulting, but it rather seems to be a conda installation problem? Conda cannot solve the environment and reports version conflicts.

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Mauricio 'Pachá' Vargas Sepúlveda / @pachadotdev:
yes, it's a conda problem, actually
there are many different conflicts, such as gfortran https://github.com/ursacomputing/crossbow/runs/2445176202#step:7:3958

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Antoine Pitrou / @pitrou:
@xhochy Do you know what might be happening here?

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Joris Van den Bossche / @jorisvandenbossche:
We should probably switch to mamba, which in addition to being faster also gives more comprehensible version conflict messages.

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Joris Van den Bossche / @jorisvandenbossche:
I tried to mimick the different "conda install" steps from the docker builds locally with mamba, and then it gives this conflict:

Problem: package gdb-9.2-py38h615daac_5 requires python >=3.8,<3.9.0a0, but none of the providers can be installed

And there is indeed not yet a gdb package available for Python3.9 (but so I am a bit unsure why this actually worked before)

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Joris Van den Bossche / @jorisvandenbossche:
Ah, it never did work. The 3.9 build was only added recently in Krisztian's refactor (ARROW-12263) and failed from the beginning.

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Antoine Pitrou / @pitrou:
Uh... why does gdb depend on the installed Python version???

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Antoine Pitrou / @pitrou:
Also, we shouldn't need gdb to build a conda package...

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Joris Van den Bossche / @jorisvandenbossche:

Uh... why does gdb depend on the installed Python version???

Because the gdb package from conda-forge includes the python extensions/support.

Also, we shouldn't need gdb to build a conda package...

gdb gets added in the "parent" conda-cpp docker build, and was added in ARROW-7119 (#6202) to provide better backtraces in the C++ tests

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Antoine Pitrou / @pitrou:
Ah, we use gdb for automatic backtraces on CI crashes...

If we want to fix this without waiting for conda-forge, we can simply install the gdb from Ubuntu (in ci/docker/conda.dockerfile) instead of conda-forge.

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Krisztian Szucs / @kszucs:
Issue resolved by pull request 10185
#10185