If svn update fails with: not authenticate to server: rejected Basic challenge, as in:

Working Directory: /home/www/cvswww/robotics.eecs.berkeley.edu/ehumans
Command:


/home/www/bin/vc-svn update --username vc@robotics.eecs.berkeley.edu --config-dir /home/vc/.subversion-robotics 2>&1 

Updating module ehumans:
     Authentication realm: UCB/EECS Subversion Repository 
     Password for 'vc@robotics.eecs.berkeley.edu': Authentication realm: UCB/EECS Subversion Repository 
     Username: svn: OPTIONS of 'https://repo.eecs.berkeley.edu/svn/projects/robotics/ehumans/trunk/ehumans/web': authorization failed: Could not authenticate to server: rejected Basic challenge (https://repo.eecs.berkeley.edu) 
Done!

root@moog robotics]# su - webuser
[webuser@moog ~]$ cd ~www/cvswww/robotics/
[webuser@moog robotics]$ ls
ehumans  robotics
[webuser@moog robotics]$ cd ehumans
[webuser@moog ehumans]$ /home/www/bin/vc-svn update --username vc@robotics.eecs.berkeley.edu --config-dir /home/vc/.subversion-robotics
Authentication realm:  UCB/EECS Subversion Repository
Password for 'vc@robotics.eecs.berkeley.edu':

-----------------------------------------------------------------------
ATTENTION!  Your password for authentication realm:

    UCB/EECS Subversion Repository

can only be stored to disk unencrypted!  You are advised to configure
your system so that Subversion can store passwords encrypted, if
possible.  See the documentation for details.

You can avoid future appearances of this warning by setting the value
of the 'store-plaintext-passwords' option to either 'yes' or 'no' in
'/home/vc/.subversion-robotics/servers'.
-----------------------------------------------------------------------
Store password unencrypted (yes/no)? yes
U    index.html
Updated to revision 79.
[webuser@moog ehumans]$