Do not crash if remote file does not exist

[Jakuje]

SUMMARY

The uninitialized pointer caused pylibssh crashing when the scp.get() failed in the first invocation of libssh.ssh_scp_pull_request() (generally when the remote file did not exist, or it was not possible to read it for some reason).

This is the full log from libssh when pytest is executed directly with the -s argument:

[2024/06/21 16:04:37.620775, 2] ssh_scp_pull_request:  Received SCP request: 'scp: /tmp/pytest-of-jjelen/pytest-22/popen-gw1/test_get_missing_src0/non-existing.txt: No such file or directory'
[2024/06/21 16:04:37.620779, 1] ssh_scp_pull_request:  SCP: Warning: scp: /tmp/pytest-of-jjelen/pytest-22/popen-gw1/test_get_missing_src0/non-existing.txt: No such file or directory
free(): invalid pointer
Fatal Python error: Aborted

(running the test from tox showed just the last line with pytest crashing)

Fixes #208
Fixes #325

ISSUE TYPE

• Bugfix Pull Request

[packit-as-a-service]

Congratulations! One of the builds has completed. 🍾

You can install the built RPMs by following these steps:

• sudo yum install -y dnf-plugins-core on RHEL 8
• sudo dnf install -y dnf-plugins-core on Fedora
• dnf copr enable packit/ansible-pylibssh-620
• And now you can install the packages.

Please note that the RPMs should be used only in a testing environment.

[webknjaz]

Overall, I like the fix and the test. Let's move the unrelated stuff out and merge it. I hope this will also address the flakiness of some tests...

[webknjaz]

@Jakuje could you also check if this is going to help with #222 / #208?

[webknjaz]

@Jakuje I just realized that we need to link the change note to #325 as well, and I wanted to give you a chance to clean up the branch after my changes. So I'm approving the PR but will wait for the final touches from you before hitting merge.

[Jakuje]

@Jakuje could you also check if this is going to help with #222 / #208?

Likely the #208 but most likely not the #222 as the SFTP goes through different code path as far as I know. I will squash the fixups now.

[Jakuje]

Should be "cleaned up". Let me know if there would be some other issues.

[KB-perByte]

Thanks for fixing this @Jakuje

[webknjaz]

@Jakuje thank you! I enabled auto-merge, it'll get into devel once the CI completes.

[webknjaz]

@Jakuje @KB-perByte this has been released as a part of v1.2.1: https://github.com/ansible/pylibssh/releases/tag/v1.2.1 / #613 / https://pypi.org/project/ansible-pylibssh/1.2.1/.

Enjoy! 🎉

[Jakuje]

Thank you for the patience in getting this to the standard :)

[webknjaz]

No problem ;) I actually enjoy helping contributors who maintain such a quality in their PRs.