Ruby interpreter complains. During builds against glibc version 2.23, an error report mentioned that implicit conversion of nil to an empty string is not automatic.
Build failure during test phase. When built against glibc version 2.23, the provided tests fail completely. The cause turns out to be a segmentation fault in the rule interpreter. The upstream code implicitly depends on a counter field being zeroed at return from malloc. Instead use calloc() for the large structures. http://bugs.debian.org/831270
