imaplib: comment on use of unbuffered pipes

Author: foresto

Lib/imaplib.py

@@ -1703,7 +1703,7 @@ def open(self, host=None, port=None, timeout=None):
         self.sock = None
         self.file = None
         self.process = subprocess.Popen(self.command,
-            bufsize=0,
+            bufsize=0,  # Unbuffered stdin/stdout, for select() compatibility
             stdin=subprocess.PIPE, stdout=subprocess.PIPE,
             shell=True, close_fds=True)
         self.writefile = self.process.stdin