Improve test for unrecognized options

Yargs 7 changed the error format and the test no longer passed.
Improve the test to avoid relying on the error format.

Signed-off-by: Kevin Locke <kevin@kevinlocke.name>

Author: kevinoid

test/swagger-spec-validator-cmd.js

@@ -313,10 +313,10 @@ describe('swagger-spec-validator command', function() {
   expectArgsResult(['-u'], 3, null, /missing|not enough/i);
   expectArgsResult(['--url'], 3, null, /missing|not enough/i);
   expectArgsResult(
-    ['--unknown'],
+    ['--badtestopt'],
     3,
     null,
-    /\b(unknown|recognized|unsupported)\b.+--unknown\b/i
+    /\bbadtestopt\b/i
   );
 
   expectArgsResult(['--help'], 0, /usage/i, null);