Swap to .lines().next() instead of .split_once('\n')

[matt-o-how]

Fixes a bug in the tests on Windows.

[coveralls-official]

Pull Request Test Coverage Report for Build 8525453606

Warning: This coverage report may be inaccurate.

This pull request's base commit is no longer the HEAD commit of its target branch. This means it includes changes from outside the original pull request, including, potentially, unrelated coverage changes.

• For more information on this, see Tracking coverage changes with pull request builds.
• To avoid this issue with future PRs, see these Recommended CI Configurations.
• For a quick fix, rebase this PR at GitHub. Your next report should be accurate.

Details

• 1 of 1 (100.0%) changed or added relevant line in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 85.451%

---

Totals
Change from base Build 8441232068:	0.0%
Covered Lines:	11277
Relevant Lines:	13197

---

💛 - Coveralls