[FIX] delivery_postlogistics: raise exception when no token received

Sometimes due to API error it may happen we don't receive anything back when requesting token.
In this case we want to show meaningful message.

delivery_postlogistics/postlogistics/web_service.py

@@ -9,11 +9,13 @@
 import urllib.parse
 from datetime import datetime, timedelta
 from io import BytesIO
+from json import JSONDecodeError
 
 import requests
 from PIL import Image
 
 from odoo import _, exceptions
+from odoo.exceptions import UserError
 
 _logger = logging.getLogger(__name__)
 
@@ -450,7 +452,22 @@ def _request_access_token(cls, delivery_carrier):
             },
             timeout=60,
         )
-        return response.json()
+
+        try:
+            response.raise_for_status()
+            json_response = response.json()
+        except (
+            JSONDecodeError,
+            requests.exceptions.HTTPError,
+        ) as error:
+            raise UserError(
+                _(
+                    "Postlogistics service is not accessible at the moment. Error code: %s. "
+                    "Please try again later." % (response.status_code or "None")
+                )
+            ) from error
+
+        return json_response
 
     @classmethod
     def get_access_token(cls, picking_carrier):

delivery_postlogistics/tests/fixtures/cassettes/test_token_error.yaml

@@ -0,0 +1,36 @@
+interactions:
+- request:
+    body: client_secret=c70e3696ae5146e7fe317434e50a90cd&grant_type=client_credentials&client_id=865783331e39e91e633c3916fe892d92
+    headers:
+      Accept:
+        - "*/*"
+      Accept-Encoding:
+        - gzip, deflate
+      Connection:
+        - keep-alive
+      Content-Length:
+        - "144"
+      User-Agent:
+        - python-requests/2.20.0
+      content-type:
+        - application/x-www-form-urlencoded
+    method: POST
+    uri: https://wedecint.post.ch/WEDECOAuth/token
+  response:
+    body:
+      string: ''
+    headers:
+      Cache-Control:
+        - no-cache; private
+      Connection:
+        - Close
+      Content-Length:
+        - "0"
+      Content-Type:
+        - text/html; charset=UTF-8
+      Date:
+        - Tue, 13 Oct 2020 10:52:26 GMT
+    status:
+      code: 503
+      message: Service Unavailable
+version: 1

delivery_postlogistics/tests/test_postlogistics.py

@@ -4,6 +4,8 @@
 
 from vcr import VCR
 
+from odoo.exceptions import UserError
+
 from .common import TestPostlogisticsCommon
 
 recorder = VCR(
@@ -108,3 +110,9 @@ def test_postlogistics_rate_shipment(self):
             res = self.carrier.postlogistics_rate_shipment(None)
             self.assertEqual(len(cassette.requests), 2)
         self.assertEqual(res["price"], 1.0)
+
+    def test_postlogistics_get_token_error(self):
+        with recorder.use_cassette("test_token_error") as cassette:
+            with self.assertRaises(UserError):
+                self.service_class._request_access_token(self.carrier)
+                self.assertEqual(len(cassette.requests), 1)