Add a function to open a file with specific permission bits

This uses the "opener" argument to open to pass extra arguments through
to os.open.

pyanaconda/iutil.py

@@ -1343,3 +1343,19 @@ def open(*args, **kwargs):  # pylint: disable=redefined-builtin
        high-level languages handle this for you, like C's fopen.
     """
     return eintr_retry_call(_open, *args, **kwargs)
+
+def open_with_perm(path, mode='r', perm=0o777, **kwargs):
+    """Open a file with the given permission bits.
+
+       This is more or less the same as using os.open(path, flags, perm), but
+       with the builtin open() semantics and return type instead of a file
+       descriptor.
+
+       :param str path: The path of the file to be opened
+       :param str mode: The same thing as the mode argument to open()
+       :param int perm: What permission bits to use if creating a new file
+    """
+    def _opener(path, open_flags):
+        return eintr_retry_call(os.open, path, open_flags, perm)
+
+    return open(path, mode, opener=_opener, **kwargs)

tests/pyanaconda_tests/iutil_test.py

@@ -771,3 +771,23 @@ def parent_dir_test(self):
 
         for d, r in dirs:
             self.assertEquals(iutil.parent_dir(d), r)
+
+    def open_with_perm_test(self):
+        """Test the open_with_perm function"""
+        # Create a directory for test files
+        test_dir = tempfile.mkdtemp()
+        try:
+            # Reset the umask
+            old_umask = os.umask(0)
+            try:
+                # Create a file with mode 0777
+                iutil.open_with_perm('test1', 'w', 0o777)
+                self.assertEqual(os.stat('test1').st_mode & 0o777, 0o777)
+
+                # Create a file with mode 0600
+                iutil.open_with_perm('test2', 'w', 0o600)
+                self.assertEqual(os.stat('test2').st_mode & 0o777, 0o600)
+            finally:
+                os.umask(old_umask)
+        finally:
+            shutil.rmtree(test_dir)