Fix error message: output port at which port finder failed to find an open port

Allows promise and callback versions of the api to both provide the
port at which they failed at in their error message. This could also
be done by changing the promise resolver to take the ports array but
that seems superfluous.

Author: eriktrom

lib/portfinder.js

@@ -198,7 +198,7 @@ internals.getPort = function (options, callback) {
         return callback(null, openPorts[0]);
       }
       else {
-        const msg = 'No open ports found in between '+ options.startPort + ' and ' + options.stopPort;
+        const msg = `Searching for an open port failed at port ${openPorts[0]}.`;
         return callback(Error(msg));
       }
     } else {

test/port-finder-multiple.test.js

@@ -58,14 +58,14 @@ describe('with 5 existing servers', function () {
           })
           .catch(function (err) {
             expect(err).not.toBeNull();
-            expect(err.message).toEqual('No open ports found in between 32768 and 32774');
+            expect(err.message).toEqual('Searching for an open port failed at port 32775.');
             done();
           });
       } else {
         method(3, { stopPort: 32774 }, function (err, ports) {
           expect(err).not.toBeNull();
-          expect(err.message).toEqual('No open ports found in between 32768 and 32774');
-          expect(ports).toEqual([32773, 32774, undefined]);
+          expect(err.message).toEqual('Searching for an open port failed at port 32775.');
+          expect(ports).toEqual([32773, 32774, undefined]); // Failed at port 32775
           done();
         });
       }

test/port-finder.test.js

@@ -82,13 +82,13 @@ describe('with 5 existing servers', function () {
           })
           .catch(function (err) {
             expect(err).not.toBeNull();
-            expect(err.message).toEqual('No open ports found in between 32768 and 32772');
+            expect(err.message).toEqual('Searching for an open port failed at port 32773.');
             done();
           });
       } else {
         method({ stopPort: 32772 }, function (err, port) {
           expect(err).not.toBeNull();
-          expect(err.message).toEqual('No open ports found in between 32768 and 32772');
+          expect(err.message).toEqual('Searching for an open port failed at port 32773.');
           expect(port).toBeUndefined();
           done();
         });