yaz.so

After a fresh, vanilla install of Bolt 1.6 on Rackspace Cloud Sites with PHP 5.4, I get this message:
Looks like the image attached to this post.
This only shows up after I log in. From that point, it shows this message whenever loading the index at /, or the admin area at /bolt.
I searched for "yaz" in the issues and the source code, and didn't see any mention. https://github.com/bolt/bolt/issues
Whoops \ Exception \ ErrorException
PHP Startup: Unable to load dynamic library '/usr/lib64/php/modules/yaz.so' - /usr/lib64/php/modules/yaz.so: undefined symbol: pval_destructor
Looks like the image attached to this post.
This only shows up after I log in. From that point, it shows this message whenever loading the index at /, or the admin area at /bolt.
I searched for "yaz" in the issues and the source code, and didn't see any mention. https://github.com/bolt/bolt/issues