Add os.sep

Lib/os.py

@@ -1,5 +1,10 @@
 from _os import *
 
+if name == 'nt':
+    sep = '\\'
+else:
+    sep = '/'
+
 # Change environ to automatically call putenv(), unsetenv if they exist.
 from _collections_abc import MutableMapping
 

tests/snippets/stdlib_os.py

@@ -58,3 +58,8 @@ if os.name == "posix":
 	os.putenv(ENV_KEY, ENV_VALUE)
 	os.unsetenv(ENV_KEY)
 	assert os.getenv(ENV_KEY) == None
+
+if os.name == "nt":
+	assert os.sep == "\\"
+else:
+	assert os.sep == "/"