I miss this functionality in pagegenerators.py. It would be super-useful to have an opposite for -ns generator.

Current approach
-ns:0,1,2,3,5,6,7,8,9,10,11,12,13,14,15,100,101,102,103,828,829,446,447

Proposed functionality
-exceptns:4

What this proposed parameter should do:

1. Call API to get list of all namespaces on current lang.family
2. Exclude ns specified in -exceptns
3. Run generator as if -ns:0,1,2,3,5,6,7,8,9,10,11,12,13,14,15,100,101,102,103,828,829,446,447 was specified