**Describe the bug**
Unit test case failed :
  1) supports http with nodejs
       should pass errors for a failed stream:
     Error: Timeout of 30000ms exceeded. For async tests and hooks, ensure "done()" is called; if returning a Promise, ensure it resolves. (***************...

**To Reproduce**
Use VS Code internal terminal to excute the unit test .

**Expected behavior**
UT should be excuted correctly.

**Environment:**
 - Axios Version: latest master
 - OS Version: Window 10

**Additional context/Screenshots**
![Capture](https://user-images.githubusercontent.com/46782518/70436361-136c5380-1ac4-11ea-87b5-203b2e46ebbf.PNG)

test/unit/adapters/http.js
});
  it('should pass errors for a failed stream', function (done) {
    server = http.createServer(function (req, res) {
      req.pipe(res);
    }).listen(4444, function () {
      axios.post('http://localhost:4444/',
        fs.createReadStream('/does/not/exist')
      ).then(function (res) {
        assert.fail();
      }).catch(function (err) {
        assert.equal(err.message, 'ENOENT: no such file or directory, open \'/does/not/exist\'');
        done();
      });
    });
  });
  it('should support buffers', function (done) {
    var buf = Buffer.alloc(1024, 'x'); // 
    server = http.createServer(function (req, res) {
      assert.equal(req.headers['content-length'], buf.length.toString());
      req.pipe(res);
    }).listen(4444, function () {
      axios.post('http://localhost:4444/',
        buf, {
          responseType: 'stream'
        }).then(function (res) {
          var stream = res.data;
          var string = '';
          stream.on('data', function (chunk) {
            string += chunk.toString('utf8');
          });