Forward underlying system package manager error messages

[perseoGI]

Changelog: Fix: Forward underlying system package manager error messages
Docs: omit

Mind that Conan behavior changes a little bit with this PR, by throwing an early exception if the system package manager is not detected by default (and not configured by config) and also, if the package manager is not found in path @memsharded

Close #19854

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• If the issue has missing info, explain the purpose/use case/pain/need that covers this Pull Request.
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[memsharded]

Looks good

[franramirez688]

@perseoGI could you include a real native log showing the new output in the Changelog? It helps a lot to see a real case instead of the mock ones (which are fine for sure)

[perseoGI]

@perseoGI could you include a real native log showing the new output in the Changelog? It helps a lot to see a real case instead of the mock ones (which are fine for sure)

@franramirez688 here you have a real example:

[AbrilRBS]

Looks way better now!

[franramirez688]

Thanks @perseoGI 👏

IMO, it reads a bit weird:

ERROR: xxxxxx
       xxxxxx
sdterr: xxxxxxx

Wdyt? I was thinking something like:

ERROR: xxxxxx
       xxxxxx
       sdterr: xxxxxxx

Or simply removing the stderr: prefix?

[memsharded]

IMO, it reads a bit weird:

It depends, if you tab the stderr message into the rest of the Conan error message (the ConanException printing), my experience is the opposite, the users will read worse the actual underlying cause of the error (like "pacman" not being installed).

In any case, this is quite an unlikely event, so the formatting is not critical, I am fine with whatever format is used.