[2.7] bpo-33542: Ignore DUID in uuid.get_node on Windows. (GH-6922) (GH-7015)

uuid._ipconfig_getnode did not validate the maximum length of the value,
so long as the value had the same type of formatting as a MAC address.
This let it select DUIDs as MAC addresses. It now requires an exact
length match..
(cherry picked from commit c66c342cb42ab8a88884527ddfe3a5086bc06316)

Co-authored-by: CtrlZvi <viz+github@flippedperspective.com>
diff --git a/Misc/ACKS b/Misc/ACKS
index 394fbb9..295b933 100644
--- a/Misc/ACKS
+++ b/Misc/ACKS
@@ -381,6 +381,7 @@
 David Edelsohn
 John Edmonds
 Grant Edwards
+Zvi Effron
 John Ehresman
 Tal Einat
 Eric Eisner
diff --git a/Misc/NEWS.d/next/Library/2018-05-16-09-30-27.bpo-33542.idNAcs.rst b/Misc/NEWS.d/next/Library/2018-05-16-09-30-27.bpo-33542.idNAcs.rst
new file mode 100644
index 0000000..16ba799
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2018-05-16-09-30-27.bpo-33542.idNAcs.rst
@@ -0,0 +1,2 @@
+Prevent ``uuid.get_node`` from using a DUID instead of a MAC on Windows.
+Patch by Zvi Effron