Description of problem:
The --append long option does not seem to work at all.  The equivelent -a option
does work.  I'm leaving this as normal severity rather than low

Version-Release number of selected component (if applicable):
Version     : 4.0.17
Release     : 11.fc6 

How reproducible:
every time

Steps to Reproduce:
1. groupadd -r sound 
2. usermod -a -G sound mikedlr
3. usermod --append -G sound mikedlr
4. usermod -a -G sound mikedlr  

Actual results:
the second and fourth command complete correctly and silently.  The third step
outputs the usage information from usermod 

Expected results:
according to manual page and usermod --help, --append option should do the same
as -a

Additional info:
I'm leaving this as normal severity since an important script might be depending
on this.