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

platformio/commands/run/helpers.py

@@ -53,9 +53,12 @@ def clean_build_dir(build_dir, config):
 
     if isdir(build_dir):
         # check project structure
-        if isfile(checksum_file) and fs.get_file_contents(checksum_file) == checksum:
-            return
+        if isfile(checksum_file):
+            with open(checksum_file) as fp:
+                if fp.read() == checksum:
+                    return
         fs.rmtree(build_dir)
 
     makedirs(build_dir)
-    fs.write_file_contents(checksum_file, checksum)
+    with open(checksum_file, "w") as fp:
+        fp.write(checksum)