bpo-27103: regrtest disables -W if -R is used (#1651)

Workaround for a regrtest bug.

Lib/test/libregrtest/cmdline.py

@@ -345,5 +345,10 @@ def _parse_args(args, **kwargs):
         ns.randomize = True
     if ns.verbose:
         ns.header = True
+    if ns.huntrleaks and ns.verbose3:
+        ns.verbose3 = False
+        print("WARNING: Disable --verbose3 because it's incompatible with "
+              "--huntrleaks: see http://bugs.python.org/issue27103",
+              file=sys.stderr)
 
     return ns