Auto merge of #12900 - pathway27:master, r=notriddle

./mach throws error on poor connectivity

<!-- Please describe your changes on the following line: -->

Imported error from socket using `from` since it's the only thing we need.
The exception is [different ](https://docs.python.org/2/library/socket.html#socket.error) from the other exceptions as it could be a string or a tuple with error number.

---
<!-- Thank you for contributing to Servo! Please replace each `[ ]` by `[X]` when the step is complete, and replace `__` with appropriate data: -->
- [X] `./mach build -d` does not report any errors
- [X] `./mach test-tidy` does not report any errors
- [X] These changes fix #12764

<!-- Either: -->
- [ ] There are tests for these changes OR
- [X] These changes do not require tests they execute before the test runner is installed. Can't test the bootstrapping code.

<!-- Pull requests that do not address these steps are welcome, but they will require additional verification as part of the review process. -->

<!-- Reviewable:start -->
---
This change is [<img src="https://reviewable.io/review_button.svg" height="34" align="absmiddle" alt="Reviewable"/>](https://reviewable.io/reviews/servo/servo/12900)
<!-- Reviewable:end -->

0 files changed, 0 insertions, 0 deletions