apache log error

gistfile1.txt

[Mon Apr 27 15:32:39.145625 2015] [:error] [pid 20302:tid 140109699139328] [remote 127.0.0.1:11740] mod_wsgi (pid=20302): Exception occurred processing WSGI script '/src/st2/st2auth/st2auth/wsgi.py'.
[Mon Apr 27 15:32:39.145665 2015] [:error] [pid 20302:tid 140109699139328] [remote 127.0.0.1:11740] Traceback (most recent call last):
[Mon Apr 27 15:32:39.145692 2015] [:error] [pid 20302:tid 140109699139328] [remote 127.0.0.1:11740]   File "/src/st2/st2auth/st2auth/wsgi.py", line 28, in <module>
[Mon Apr 27 15:32:39.145776 2015] [:error] [pid 20302:tid 140109699139328] [remote 127.0.0.1:11740]     username=username, password=password)
[Mon Apr 27 15:32:39.145790 2015] [:error] [pid 20302:tid 140109699139328] [remote 127.0.0.1:11740]   File "/src/st2/st2common/st2common/models/db/__init__.py", line 29, in db_setup
[Mon Apr 27 15:32:39.145878 2015] [:error] [pid 20302:tid 140109699139328] [remote 127.0.0.1:11740]     username=username, password=password)
[Mon Apr 27 15:32:39.145891 2015] [:error] [pid 20302:tid 140109699139328] [remote 127.0.0.1:11740]   File "/src/st2/virtualenv/lib/python2.7/site-packages/mongoengine/connection.py", line 164, in connect
[Mon Apr 27 15:32:39.145981 2015] [:error] [pid 20302:tid 140109699139328] [remote 127.0.0.1:11740]     return get_connection(alias)
[Mon Apr 27 15:32:39.145994 2015] [:error] [pid 20302:tid 140109699139328] [remote 127.0.0.1:11740]   File "/src/st2/virtualenv/lib/python2.7/site-packages/mongoengine/connection.py", line 126, in get_connection
[Mon Apr 27 15:32:39.146016 2015] [:error] [pid 20302:tid 140109699139328] [remote 127.0.0.1:11740]     raise ConnectionError("Cannot connect to database %s :\\n%s" % (alias, e))
[Mon Apr 27 15:32:39.146036 2015] [:error] [pid 20302:tid 140109699139328] [remote 127.0.0.1:11740] ConnectionError: Cannot connect to database default :
[Mon Apr 27 15:32:39.146042 2015] [:error] [pid 20302:tid 140109699139328] [remote 127.0.0.1:11740] False is not a read preference.