Make block_device fixture return str instead of pathlib.Path

This is done because `pathlib.Path` automatically adds a trailing
backslash to Windows paths of the shape `\\.\PhysicalDriveN`.
Trying to open such a path including the trailing backslash raises
`PermissionError`. This issue is tracked at python/cpython#78079.

tests/conftest.py

@@ -58,7 +58,7 @@ def block_device(request, tempdir):
             encoding='utf-8',
         )
         device_path = completed_process.stdout.rstrip()
-        yield Path(device_path)
+        yield device_path
 
         # Clean up
         subprocess.run(
@@ -84,7 +84,7 @@ def block_device(request, tempfile):
             encoding='utf-8',
         )
         device_path = completed_process.stdout.rstrip()
-        yield Path(device_path)
+        yield device_path
 
         # Clean up
         subprocess.run(['losetup', '-d', device_path])
@@ -107,5 +107,5 @@ def block_device(request, tempfile):
 logical or physical sector size for a virtual block device. In that case,
 values which cannot be used are ignored.
 
-Returns a ``pathlib.Path`` object representing the path of the block device.
+Returns a string representing the path of the block device.
 """

tests/test_platform_specific.py

@@ -58,7 +58,7 @@ def test_device_properties(block_device, size_expected, sector_size_expected) ->
     """Test that ``device_size()`` and ``device_sector_size()`` return the expected
     values.
     """
-    with block_device.open('rb') as f:
+    with open(block_device, 'rb') as f:
         size_actual = platform_specific.device_size(f)
         sector_size_actual = platform_specific.device_sector_size(f)
 
@@ -86,5 +86,5 @@ def test_reread_partition_table(block_device):
     """Test that correctly invoking ``reread_partition_table()`` does not raise an
     exception.
     """
-    with block_device.open('rb') as f:
+    with open(block_device, 'rb') as f:
         platform_specific.reread_partition_table(f)