This comes from the fact that while viewvc was parsing /etc/tuleap/conf/local.inc, it encountered a syntax error:

Traceback (most recent call last):
  File "/var/www/cgi-bin/viewvc.cgi", line 57, in ?
    import viewvc
  File "/usr/share/viewvc/lib/viewvc.py", line 62, in ?
    import include
  File "/usr/share/codendi/src/www/../utils/include.py", line 58, in ?
    load_local_config(db_include)
  File "/usr/share/codendi/src/www/../utils/include.py", line 45, in load_local_config
    exec n in globals()
  File "<string>", line 1
    sys_max_size_upload = 4194304000;// 67108864

By editing local.inc to add a space between the semicolon and the comment, all went fine:

# Before
$sys_max_size_upload = 4194304000;// 67108864;
# After
$sys_max_size_upload = 4194304000; // 67108864;