Corrected the Content-Type header for /basePath/swagger.json to retur…

…n application/json and added a test for that

connexion/api.py

@@ -222,7 +222,9 @@ def add_swagger_json(self):
         """
         logger.debug('Adding swagger.json: %s/swagger.json', self.base_url)
         endpoint_name = "{name}_swagger_json".format(name=self.blueprint.name)
-        self.blueprint.add_url_rule('/swagger.json', endpoint_name, lambda: json.dumps(self.specification))
+        self.blueprint.add_url_rule('/swagger.json',
+                                    endpoint_name,
+                                    lambda: flask.jsonify(self.specification))
 
     def add_swagger_ui(self):
         """

tests/api/test_bootstrap.py

@@ -72,6 +72,14 @@ def test_no_swagger_json_api(simple_api_spec_dir):
     assert swagger_json.status_code == 404
 
 
+def test_swagger_json_content_type(simple_app):
+    app_client = simple_app.app.test_client()
+
+    response = app_client.get('/v1.0/swagger.json', data={})  # type: flask.Response
+    assert response.status_code == 200
+    assert response.content_type == 'application/json'
+
+
 def test_single_route(simple_app):
     def route1():
         return 'single 1'