refactore: add string template for api url

config.yml

@@ -1,5 +1,5 @@
 api:
-  url: https://api.transilien.com/gare/{departure_station}/depart/{arrival_station}
+  url: https://api.transilien.com/gare/${departure_station}/depart/${arrival_station}
   departure_station: 00000000
   arrival_station: 00000000
   user: user

rerwatcher/api.py

@@ -8,6 +8,7 @@
 """
 
 from datetime import datetime
+from string import Template
 
 import requests
 from lxml import etree
@@ -66,7 +67,7 @@ class TransilienApi:
             'encoding'.
 
     Attributes:
-        _url (str): https://api.transilien.com/gare/{departure_station}/depart/{arrival_station}
+        _url (str): https://api.transilien.com/gare/${departure_station}/depart/${arrival_station}
         _auth (HTTPBasicAuth): the basic authentication built with the
             user and password config params.
         _date_format (str): '%d/%m/%Y %H:%M'
@@ -75,7 +76,8 @@ class TransilienApi:
     """
 
     def __init__(self, config):
-        self._url = config['api']['url'].format(
+        url_template = Template(config['api']['url'])
+        self._url = url_template.substitute(
             departure_station=config['api']['departure_station'],
             arrival_station=config['api']['arrival_station']
         )

tests/conftest.py

@@ -8,7 +8,7 @@
 def fake_config():
     return {
         "api": {
-            "url": 'https://test.url/{departure_station}/depart/{arrival_station}',
+            "url": 'https://test.url/${departure_station}/depart/${arrival_station}',
             "departure_station": 123,
             "arrival_station": 321,
             "user": 'user',

tests/test_rerwatcher.py

@@ -2,6 +2,7 @@
 # coding: utf-8
 
 import os
+from string import Template
 from unittest.mock import patch
 
 from requests.auth import HTTPBasicAuth
@@ -29,7 +30,7 @@ def test_build_rer_watcher_return_app(load_config, fake_config):
     assert isinstance(app, RerWatcher)
     assert app._refresh_time == fake_config['refresh_time']['default']
     assert isinstance(app._api, TransilienApi)
-    assert app._api._url == fake_config['api']['url'].format(
+    assert app._api._url == Template(fake_config['api']['url']).substitute(
         departure_station=fake_config['api']['departure_station'],
         arrival_station=fake_config['api']['arrival_station'],
     )