"/_" cannot be opened with mode "a"

Stack Trace:

#0 /data/ServiceChampion.git/website/easycuc/application/Bootstrap.php(57): Zend_Log_Writer_Stream->__construct()
#1 /data/ZF1.git/library/Zend/Application/Bootstrap/BootstrapAbstract.php(681): Bootstrap->_initLogger()
#2 /data/ZF1.git/library/Zend/Application/Bootstrap/BootstrapAbstract.php(634): Zend_Application_Bootstrap_BootstrapAbstract->_executeResource()
#3 /data/ZF1.git/library/Zend/Application/Bootstrap/BootstrapAbstract.php(598): Zend_Application_Bootstrap_BootstrapAbstract->_bootstrap()
#4 /data/ZF1.git/library/Zend/Application.php(373): Zend_Application_Bootstrap_BootstrapAbstract->bootstrap()
#5 /data/ServiceChampion.git/website/public_html/easycuc/index_zf.php(68): Zend_Application->bootstrap()
#6 /data/ServiceChampion.git/website/public_html/easycuc/index.php(16): include('/data/ServiceChampion.git/website/public_html/easycuc/index_zf.php')
#6 {main}