Update docstrings w.r.t. subprocess2.

subprocess2.py

Index: subprocess2.py
diff --git a/subprocess2.py b/subprocess2.py
index 4ba3c65abc864ad6a1dbe1b7fadab71d5cd9d20a..5678127aff4e96c1f60e114eec6a2012f9e828b9 100644
--- a/subprocess2.py
+++ b/subprocess2.py
@@ -132,7 +132,7 @@ def get_english_env(env):
 
 
 def Popen(args, **kwargs):
-  """Wraps subprocess.Popen().
+  """Wraps subprocess.Popen() with various workarounds.
 
   Returns a subprocess.Popen object.
 
@@ -142,7 +142,8 @@ def Popen(args, **kwargs):
     shell parameter to a value.
   - Adds support for VOID to not buffer when not needed.
 
-  Note: Popen() can throw OSError when cwd or args[0] doesn't exist.
+  Note: Popen() can throw OSError when cwd or args[0] doesn't exist. Translate
+  exceptions generated by cygwin when it fails trying to emulate fork().
   """
   # Make sure we hack subprocess if necessary.
   hack_subprocess()