Django raises NoReverseMatch: 'en-us' is not a registered namespace
NoReverseMatch error has to do with urls so check your url patterns 
url(...). 
make sure your django version is 1.11 if not try to update it to 1.11
Django raises

django.urls.exceptions.NoReverseMatch: 'en-us' is not a registered namespace

How i can fix it?