Fix Pylint warnings.

tests/test_requirements.py

@@ -1,13 +1,15 @@
 """
 Check whether `requirements.txt` contains all requirements from `setup.py`.
 """
-from map_machine import REQUIREMENTS
 from pathlib import Path
 
+from map_machine import REQUIREMENTS
+
 
 def test_requirements() -> None:
+    """Test whether `requirements.txt` has the same packages as `setup.py`."""
     requirements: list[str]
-    with Path("requirements.txt").open() as requirements_file:
+    with Path("requirements.txt").open(encoding="utf-8") as requirements_file:
         requirements = list(
             map(lambda x: x[:-1], requirements_file.readlines())
         )