Correctly generate two lines of text in the test file.

The previous version incorrectly appended the second line of text to the first. It was missing the EOL separator. This commit adds that separator.
No test results should be changed with this commit.

tests/test_hasher.py

@@ -50,7 +50,7 @@ def test_file_exists(self):
         # Add a file with contents
         file = Path(folder / "testfile.txt")
         with file.open(mode="wt") as f:
-            f.write("Some text in a file.")
+            f.write("Some text in a file.\n")
             f.write("Another line of text.")
 
         # Create an empty folder