Update URL for Python 3 information

SABnzbd.py

@@ -19,7 +19,7 @@ import sys
 
 if sys.hexversion < 0x03060000:
     print("Sorry, requires Python 3.6 or above")
-    print("You can read more at: https://sabnzbd.org/python3")
+    print("You can read more at: https://sabnzbd.org/wiki/installation/install-off-modules")
     sys.exit(1)
 
 import logging
@@ -48,7 +48,7 @@ try:
 except ImportError as e:
     print("Not all required Python modules are available, please check requirements.txt")
     print("Missing module:", e.name)
-    print("You can read more at: https://sabnzbd.org/python3")
+    print("You can read more at: https://sabnzbd.org/wiki/installation/install-off-modules")
     print("If you still experience problems, remove all .pyc files in this folder and subfolders")
     sys.exit(1)
 
@@ -68,7 +68,6 @@ from sabnzbd.misc import (
     get_serv_parms,
     get_from_url,
     upload_file_to_sabnzbd,
-    is_ipv4_addr,
     is_localhost,
     is_lan_addr,
 )