os: Add fsencode() & fsdecode().

os/metadata.txt

@@ -1,4 +1,4 @@
 srctype = micropython-lib
 type = package
-version = 0.0.7
+version = 0.0.8
 author = Paul Sokolovsky

os/os/__init__.py

@@ -159,3 +159,14 @@ def waitpid(pid, opts):
     r = waitpid_(pid, a, opts)
     check_error(r)
     return (r, a[0])
+
+
+def fsencode(s):
+    if type(s) is bytes:
+        return s
+    return bytes(s, "utf-8")
+
+def fsdecode(s):
+    if type(s) is str:
+        return s
+    return str(s, "utf-8")

os/setup.py

@@ -6,7 +6,7 @@ from setuptools import setup
 
 
 setup(name='micropython-os',
-      version='0.0.7',
+      version='0.0.8',
       description='os module for MicroPython',
       long_description="This is a module reimplemented specifically for MicroPython standard library,\nwith efficient and lean design in mind. Note that this module is likely work\nin progress and likely supports just a subset of CPython's corresponding\nmodule. Please help with the development if you are interested in this\nmodule.",
       url='https://github.com/micropython/micropython/issues/405',

os/test_fsencode.py

@@ -0,0 +1,7 @@
+import os
+
+print(os.fsencode("abc"))
+print(os.fsencode(b"abc"))
+
+print(os.fsdecode("abc"))
+print(os.fsdecode(b"abc"))