Index: Lib/subprocess.py
===================================================================
--- Lib/subprocess.py	(révision 88430)
+++ Lib/subprocess.py	(copie de travail)
@@ -1193,9 +1193,13 @@
                 if errwrite is not None and errread is not None:
                     os.close(errwrite)
 
-                # Wait for exec to fail or succeed; possibly raising exception
-                # Exception limited to 1M
-                data = _eintr_retry_call(os.read, errpipe_read, 1048576)
+                # Wait for exec to fail or succeed; possibly raising exception.
+                # The exception is unlikely: start with a buffer of 1 byte to
+                # avoid the creation of a buffer of 1 MB.
+                data = _eintr_retry_call(os.read, errpipe_read, 1)
+                if data:
+                    # Exception limited to 1M
+                    data += _eintr_retry_call(os.read, errpipe_read, 1048575)
             finally:
                 # be sure the FD is closed no matter what
                 os.close(errpipe_read)