grml2usb: remove_default_entry: avoid using fileinput

Author: zeha

grml2usb

@@ -1477,12 +1477,16 @@ def remove_default_entry(filename: str) -> None:
 
     @filename: syslinux config file
     """
-    default_re = re.compile(r"^(\s*menu\s*default\s*)$", re.I)
-    for line in fileinput.input(filename, inplace=True):
-        if default_re.match(line):
-            continue
-        sys.stdout.write(line)
-    fileinput.close()
+    default_re = re.compile(r"^(\s*menu\s*default\s*)$", re.I | re.MULTILINE)
+    lines = []
+    with open(filename, "r+") as fh:
+        for line in fh.read().split("\n"):
+            if default_re.match(line):
+                continue
+            lines.append(line)
+        fh.seek(0)
+        fh.truncate()
+        fh.write("\n".join(lines))
 
 
 def handle_syslinux_config(