fix(_handlers.ts): typo (#655)

* Fix a typo in _handlers.ts
* Fix a typo in handlers.spec.ts

Author: maple3142

src/_handlers.ts

@@ -79,7 +79,7 @@ function defaultErrorHandler(err, req: express.Request, res: express.Response) {
     }
   }
 
-  res.end(`Error occured while trying to proxy: ${host}${req.url}`);
+  res.end(`Error occurred while trying to proxy: ${host}${req.url}`);
 }
 
 function logClose(req, socket, head) {

test/unit/handlers.spec.ts

@@ -119,7 +119,7 @@ describe('default proxy error handler', () => {
 
   it('should end the response and return error message', () => {
     proxyError(mockError, mockReq, mockRes, proxyOptions);
-    expect(errorMessage).toBe('Error occured while trying to proxy: localhost:3000/api');
+    expect(errorMessage).toBe('Error occurred while trying to proxy: localhost:3000/api');
   });
 
   it('should not set the http status code to: 500 if headers have already been sent', () => {
@@ -131,7 +131,7 @@ describe('default proxy error handler', () => {
   it('should end the response and return error message', () => {
     mockRes.headersSent = true;
     proxyError(mockError, mockReq, mockRes, proxyOptions);
-    expect(errorMessage).toBe('Error occured while trying to proxy: localhost:3000/api');
+    expect(errorMessage).toBe('Error occurred while trying to proxy: localhost:3000/api');
   });
 
   it('should re-throw error from http-proxy when target is missing', () => {