bpo-39068: Fix race condition in base64 (GH-17627)

There was a race condition in base64 in lazy initialization of multiple globals.
diff --git a/Misc/ACKS b/Misc/ACKS
index 80e51f9..211455b 100644
--- a/Misc/ACKS
+++ b/Misc/ACKS
@@ -1659,6 +1659,7 @@
 Frank Stajano
 Joel Stanley
 Kyle Stanley
+Brandon Stansbury
 Anthony Starks
 David Steele
 Oliver Steele
diff --git a/Misc/NEWS.d/next/Library/2019-12-16-17-55-31.bpo-39068.Ti3f9P.rst b/Misc/NEWS.d/next/Library/2019-12-16-17-55-31.bpo-39068.Ti3f9P.rst
new file mode 100644
index 0000000..fe6503f
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2019-12-16-17-55-31.bpo-39068.Ti3f9P.rst
@@ -0,0 +1,2 @@
+Fix initialization race condition in :func:`a85encode` and :func:`b85encode`
+in :mod:`base64`. Patch by Brandon Stansbury.