bpo-36807: When saving a file in IDLE, call flush and fsync (#13102)

Lib/idlelib/iomenu.py

@@ -384,6 +384,8 @@ class IOBinding:
         try:
             with open(filename, "wb") as f:
                 f.write(chars)
+                f.flush()
+                os.fsync(f.fileno())
             return True
         except OSError as msg:
             tkMessageBox.showerror("I/O Error", str(msg),

Misc/NEWS.d/next/IDLE/2019-05-05-16-27-53.bpo-13102.AGNWYJ.rst

@@ -0,0 +1 @@
+When saving a file, call os.flush() so bits are flushed to e.g. USB drive.