Use native open/io.open for file contents reading/writing

platformio/commands/debug/helpers.py

@@ -252,12 +252,14 @@ def is_prog_obsolete(prog_path):
                 break
             shasum.update(data)
     new_digest = shasum.hexdigest()
-    old_digest = (
-        fs.get_file_contents(prog_hash_path) if isfile(prog_hash_path) else None
-    )
+    old_digest = None
+    if isfile(prog_hash_path):
+        with open(prog_hash_path) as fp:
+            old_digest = fp.read()
     if new_digest == old_digest:
         return False
-    fs.write_file_contents(prog_hash_path, new_digest)
+    with open(prog_hash_path, "w") as fp:
+        fp.write(new_digest)
     return True