Replace missed f-string with format

Author: tim-mccurrach

tests/test_views.py

@@ -15,7 +15,7 @@
 
 JSON_ERROR = 'JSON parse error - Expecting value:'
 STATUS_CODE_400 = 'Bad Request'
-REASON_PHRASE_RE = fr"{STATUS_CODE_400} \({JSON_ERROR}.*\)"
+REASON_PHRASE_RE = r"{} \({}.*\)".format(STATUS_CODE_400, JSON_ERROR)
 VALIDATION_ERROR = "Data isn't valid!"