Allows underscores in URL hosts

Author: pitbulk

src/onelogin/saml2/settings.py

@@ -25,7 +25,7 @@
 # Released under a BSD 3-Clause License
 url_regex = re.compile(
     r'^(?:[a-z0-9\.\-]*)://'  # scheme is validated separately
-    r'(?:(?:[A-Z0-9](?:[A-Z0-9-]{0,61}[A-Z0-9])?\.)+(?:[A-Z]{2,6}\.?|[A-Z0-9-]{2,}\.?)|'  # domain...
+    r'(?:(?:[A-Z0-9_](?:[A-Z0-9-_]{0,61}[A-Z0-9_])?\.)+(?:[A-Z]{2,6}\.?|[A-Z0-9-]{2,}\.?)|'  # domain...
     r'localhost|'  # localhost...
     r'\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}|'  # ...or ipv4
     r'\[?[A-F0-9]*:[A-F0-9:]+\]?)'  # ...or ipv6