fix expected error message when node 0.12.x

Author: Jeremy Judeaux

test/lib-https-proxy-test.js

@@ -166,7 +166,11 @@ describe('lib/http-proxy.js', function() {
 
         proxy.on('error', function (err, req, res) {
           expect(err).to.be.an(Error);
-          expect(err.toString()).to.be('Error: DEPTH_ZERO_SELF_SIGNED_CERT')
+          if (process.versions.node.indexOf('0.12.') == 0) {
+            expect(err.toString()).to.be('Error: self signed certificate')
+          } else {
+            expect(err.toString()).to.be('Error: DEPTH_ZERO_SELF_SIGNED_CERT')
+          }
           done();
         })