Fix test compatibility with werkzeug 0.15.x

Remove the check for `Content-Length` header that is not provided
by default anymore with werkzeug 0.15.x.

See: pallets/werkzeug#2347

Taken from postmanlabs#684

setup.py

@@ -36,6 +36,6 @@
     include_package_data = True, # include files listed in MANIFEST.in
     install_requires=[
         'Flask<1.1', 'MarkupSafe<2.1', 'decorator', 'itsdangerous<2.1', 'brotlipy',
-        'raven[flask]', 'werkzeug<0.15', 'gevent', 'flasgger', 'jinja2<3.1'
+        'raven[flask]', 'werkzeug<2', 'gevent', 'flasgger', 'jinja2<3.1'
     ],
 )

tests/test_httpbin.py

@@ -147,7 +147,6 @@ def test_get(self):
         data = json.loads(response.data.decode('utf-8'))
         self.assertEqual(data['args'], {})
         self.assertEqual(data['headers']['Host'], 'localhost')
-        self.assertEqual(data['headers']['Content-Length'], '0')
         self.assertEqual(data['headers']['User-Agent'], 'test')
         # self.assertEqual(data['origin'], None)
         self.assertEqual(data['url'], 'http://localhost/get')
@@ -161,7 +160,6 @@ def test_anything(self):
         data = json.loads(response.data.decode('utf-8'))
         self.assertEqual(data['args'], {})
         self.assertEqual(data['headers']['Host'], 'localhost')
-        self.assertEqual(data['headers']['Content-Length'], '0')
         self.assertEqual(data['url'], 'http://localhost/anything/foo/bar')
         self.assertEqual(data['method'], 'GET')
         self.assertTrue(response.data.endswith(b'\n'))