Add test capturing expectation. Ref #1451.

setuptools/tests/test_build_py.py

 import os
+import stat
+import shutil
 
 from setuptools.dist import Distribution
 
@@ -20,3 +22,28 @@ def test_directories_in_package_data_glob(tmpdir_cwd):
     os.makedirs('path/subpath')
     dist.parse_command_line()
     dist.run_commands()
+
+
+def test_read_only(tmpdir_cwd):
+    """
+    Ensure mode is not preserved in copy for package modules
+    and package data, as that causes problems
+    with deleting read-only files on Windows.
+
+    #1451
+    """
+    dist = Distribution(dict(
+        script_name='setup.py',
+        script_args=['build_py'],
+        packages=['pkg'],
+        package_data={'pkg': ['data.dat']},
+        name='pkg',
+    ))
+    os.makedirs('pkg')
+    open('pkg/__init__.py', 'w').close()
+    open('pkg/data.dat', 'w').close()
+    os.chmod('pkg/__init__.py', stat.S_IREAD)
+    os.chmod('pkg/data.dat', stat.S_IREAD)
+    dist.parse_command_line()
+    dist.run_commands()
+    shutil.rmtree('build')