diff -r 0df93ab07a8f Lib/subprocess.py
--- a/Lib/subprocess.py	Fri May 27 11:20:21 2016 +0000
+++ b/Lib/subprocess.py	Fri May 27 18:51:27 2016 -0700
@@ -1317,7 +1317,7 @@
 
                 # Wait for exec to fail or succeed; possibly raising exception
                 data = _eintr_retry_call(os.read, errpipe_read, 1048576)
-                pickle_bits = [data]
+                pickle_bits = []
                 while data:
                     pickle_bits.append(data)
                     data = _eintr_retry_call(os.read, errpipe_read, 1048576)