Fix import json_available error (#136)

* Fix import json_available broken

* Flask 1.1.0 or above remove json_available. ref: d362399e

Signed-off-by: chang-ning <spiderpower02@gmail.com>

* Add environment FLASK=1.1.0 & FLASK=1.0.2

Signed-off-by: chang-ning <spiderpower02@gmail.com>

* Add environment python3.6

Signed-off-by: chang-ning <spiderpower02@gmail.com>

.travis.yml

@@ -43,4 +43,4 @@ notifications:
   email:
     - christoph.heer@googlemail.com
     - jonathan.como@gmail.com
-version: ~> 1.0
+version: ~> 1.0

flask_testing/utils.py

@@ -35,7 +35,7 @@
 from werkzeug.utils import cached_property
 
 # Use Flask's preferred JSON module so that our runtime behavior matches.
-from flask import json_available, templating, template_rendered
+from flask import templating, template_rendered
 
 try:
     from flask import message_flashed
@@ -45,8 +45,13 @@
     message_flashed = None
     _is_message_flashed = False
 
-if json_available:
+json_available = True
+
+try:
     from flask import json
+except ImportError:
+    json_available = False
+
 
 # we'll use signals for template-related tests if
 # available in this version of Flask