add non_json_response code and fixup test

b2sdk/b2http.py

@@ -432,6 +432,7 @@ def _translate_errors(cls, fcn, post_params=None):
                         raise PotentialS3EndpointPassedAsRealm(response.content)
                     error = {
                         'message': response.content.decode('utf-8', errors='replace'),
+                        'code': 'non_json_response',
                     }
                 extra_error_keys = error.keys() - ('code', 'status', 'message')
                 if extra_error_keys:

test/unit/b2http/test_b2http.py

@@ -118,11 +118,10 @@ def test_invalid_json(self):
         response.content = b'{' * 500
         response.url = 'https://example.com'
 
-        with self.assertRaises(BadRequest) as error:
+        with pytest.raises(BadRequest) as exc_info:
             B2Http._translate_errors(lambda: response)
 
-            content_length = min(len(response.content), len(error.content))
-            self.assertEqual(response.content[:content_length], error.content[:content_length])
+        assert str(exc_info.value) == f"{response.content.decode()} (non_json_response)"
 
     def test_potential_s3_endpoint_passed_as_realm(self):
         response = MagicMock()