Fix leaking file descriptors in streamed download

[m-bucher]

Fixes #7157

RfC ;-)

[ggainey]

Can we get a CHANGES/7157.bugfix please? Thanks!

[dralley]

@m-bucher ^

[quba42]

I added a changelog and also "subscribed" to this PR, since @m-bucher is on PTO at the moment.

Feel free to ping me if anything more is needed.

[jobselko]

Do we need some backports?

[patchback]

Backport to 3.85: 💚 backport PR created

✅ Backport PR branch: patchback/backports/3.85/4307aaacd4169a78fde43e2a5cbf664e50c9ef2e/pr-7158

Backported as #7167

🤖 @patchback
I'm built with octomachinery and
my source is open — https://github.com/sanitizers/patchback-github-app.

[patchback]

Backport to 3.73: 💔 cherry-picking failed — conflicts found

❌ Failed to cleanly apply 4307aaa on top of patchback/backports/3.73/4307aaacd4169a78fde43e2a5cbf664e50c9ef2e/pr-7158

Backporting merged PR #7158 into main

1. Ensure you have a local repo clone of your fork. Unless you cloned it
   from the upstream, this would be your origin remote.
2. Make sure you have an upstream repo added as a remote too. In these
   instructions you'll refer to it by the name upstream. If you don't
   have it, here's how you can add it:

   $ git remote add upstream https://github.com/pulp/pulpcore.git

3. Ensure you have the latest copy of upstream and prepare a branch
   that will hold the backported code:

   $ git fetch upstream
   $ git checkout -b patchback/backports/3.73/4307aaacd4169a78fde43e2a5cbf664e50c9ef2e/pr-7158 upstream/3.73

4. Now, cherry-pick PR Fix leaking file descriptors in streamed download #7158 contents into that branch:

   $ git cherry-pick -x 4307aaacd4169a78fde43e2a5cbf664e50c9ef2e

   If it'll yell at you with something like fatal: Commit 4307aaacd4169a78fde43e2a5cbf664e50c9ef2e is a merge but no -m option was given., add -m 1 as follows instead:

   $ git cherry-pick -m1 -x 4307aaacd4169a78fde43e2a5cbf664e50c9ef2e

5. At this point, you'll probably encounter some merge conflicts. You must
   resolve them in to preserve the patch from PR Fix leaking file descriptors in streamed download #7158 as close to the
   original as possible.
6. Push this branch to your fork on GitHub:

   $ git push origin patchback/backports/3.73/4307aaacd4169a78fde43e2a5cbf664e50c9ef2e/pr-7158

7. Create a PR, ensure that the CI is green. If it's not — update it so that
   the tests and any other checks pass. This is it!
   Now relax and wait for the maintainers to process your pull request
   when they have some cycles to do reviews. Don't worry — they'll tell you if
   any improvements are necessary when the time comes!

🤖 @patchback
I'm built with octomachinery and
my source is open — https://github.com/sanitizers/patchback-github-app.

[patchback]

Backport to 3.95: 💚 backport PR created

✅ Backport PR branch: patchback/backports/3.95/4307aaacd4169a78fde43e2a5cbf664e50c9ef2e/pr-7158

Backported as #7166

🤖 @patchback
I'm built with octomachinery and
my source is open — https://github.com/sanitizers/patchback-github-app.