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

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 c66c342cb4)

Co-authored-by: CtrlZvi <viz+github@flippedperspective.com>

Lib/uuid.py

@@ -488,7 +488,7 @@ def _ipconfig_getnode():
         with proc:
             for line in proc.stdout:
                 value = line.split(':')[-1].strip().lower()
-                if re.match('([0-9a-f][0-9a-f]-){5}[0-9a-f][0-9a-f]', value):
+                if re.fullmatch('(?:[0-9a-f][0-9a-f]-){5}[0-9a-f][0-9a-f]', value):
                     mac = int(value.replace('-', ''), 16)
                     if _is_universal(mac):
                         return mac

Misc/ACKS

@@ -426,6 +426,7 @@ Ulrich Eckhardt
 David Edelsohn
 John Edmonds
 Grant Edwards
+Zvi Effron
 John Ehresman
 Tal Einat
 Eric Eisner

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