Fix 403 error

requirements-dev.txt

@@ -1,3 +1,4 @@
 -r requirements.txt
 jupytext
 pre-commit
+requests

tests/test_all.py

@@ -11,12 +11,13 @@
 from pathlib import Path
 import subprocess
 import sys
-import urllib.request
+import requests
 from urllib.parse import unquote
 
 from markdown import markdown as md2html
 
 
+UA = 'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/58.0.3029.110 Safari/537.3'
 ROOT = Path(__file__).parents[1]
 
 
@@ -63,13 +64,13 @@ def errm(issue):
             # Internet links
             if "http" in link:
                 try:
-                    request = urllib.request.Request(
-                        link, method="HEAD", headers={'User-Agent': 'Mozilla'})
-                    response = urllib.request.urlopen(request, timeout=2)
-                    assert response.status == 200
+                    response = requests.head(link, headers={'User-Agent': UA})
+                    # https://developer.mozilla.org/en-US/docs/Web/HTTP/Status
+                    assert response.status_code < 400
                 except Exception as e:
                     failed |= True
-                    _report_error(errm("**requesting**") + f"\nError:\n    {e}")
+                    _report_error(errm("**requesting**") +
+                        f"\nStatus code: {response.status_code}")
 
             # Local links
             else: