sagemathgh-38521: Fix `sage_bootstrap.flock` for Python 3.13 (fedora-41)
    
<!-- ^ Please provide a concise and informative title. -->
<!-- ^ Don't put issue numbers in the title, do this in the PR
description below. -->
<!-- ^ For example, instead of "Fixes sagemath#12345" use "Introduce new method
to calculate 1 + 2". -->
<!-- v Describe your changes below in detail. -->
<!-- v Why is this change required? What problem does it solve? -->
<!-- v If this PR resolves an open issue, please link to it here. For
example, "Fixes sagemath#12345". -->

Seen on Fedora 41, which already ships Python 3.13:

https://github.com/mkoeppe/sage/actions/runs/10426436105/job/28893965205
#step:11:10930
```
sagemath#28 943.2   [pip-24.0]   [spkg-pipinst]   File
"/sage/build/bin/../sage_bootstrap/flock.py", line 15, in <module>
sagemath#28 943.2   [pip-24.0]   [spkg-pipinst]     import pipes
sagemath#28 943.2   [pip-24.0]   [spkg-pipinst] ModuleNotFoundError: No module
named 'pipes'
```

### 📝 Checklist

<!-- Put an `x` in all the boxes that apply. -->

- [x] The title is concise and informative.
- [x] The description explains in detail what this PR is about.
- [ ] I have linked a relevant issue or discussion.
- [ ] I have created tests covering the changes.
- [ ] I have updated the documentation and checked the documentation
preview.

### ⌛ Dependencies

<!-- List all open PRs that this PR logically depends on. For example,
-->
<!-- - sagemath#12345: short description why this is a dependency -->
<!-- - sagemath#34567: ... -->
    
URL: sagemath#38521
Reported by: Matthias Köppe
Reviewer(s): François Bissey, Kwankyu Lee, Matthias Köppe