Fix test suite use of r.json is None

This breaks in Flask 2.2; we need to check `\.is_json` instead.

This appears to be limited to the test suite, and was causing the macOS
build failure (as that machine was recently upgraded, getting the new
Flask version in the process).

Author: jagerman

tests/test_onion_requests.py

@@ -209,9 +209,8 @@ def test_v4_authenticated(room, mod, client):
 def v4_post_body():
     from flask import request, jsonify, Response
 
-    if request.json is not None:
+    if request.is_json:
         return jsonify({"json": request.json})
-    print(f"rd: {request.data}")
     return Response(
         f"not json ({request.content_type}): {request.data.decode()}".encode(),
         mimetype='text/plain',
@@ -234,8 +233,10 @@ def test_v4_post_body(room, user, client):
 
     info, body = decrypt_reply(r.data, v=4, enc_type="xchacha20")
 
-    assert info == {'code': 200, 'headers': {'content-type': 'text/plain; charset=utf-8'}}
-    assert body == b'not json (text/plain): test data'
+    assert (info, body) == (
+        {'code': 200, 'headers': {'content-type': 'text/plain; charset=utf-8'}},
+        b'not json (text/plain): test data',
+    )
 
     # Now try with json:
     test_json = {"test": ["json", None], "1": 23}

tests/test_routes_general.py

@@ -128,7 +128,7 @@ def batch_test_endpoint3():
 def batch_test_endpoint4():
     from flask import request, jsonify, Response
 
-    if request.json is not None:
+    if request.is_json:
         return jsonify({"echo": request.json})
     return Response(f"echo: {request.data.decode()}".encode(), mimetype='text/plain')