Create ~/.pypirc securely (#13512).

There was a window between the write and the chmod where the user’s
password would be exposed, depending on default permissions.  Philip
Jenvey’s patch fixes it.
diff --git a/Misc/ACKS b/Misc/ACKS
index fed0553..548279a 100644
--- a/Misc/ACKS
+++ b/Misc/ACKS
@@ -412,6 +412,7 @@
 Thomas Jarosch
 Drew Jenkins
 Flemming Kjær Jensen
+Philip Jenvey
 Jiba
 Orjan Johansen
 Fredrik Johansson