To reproduce build from latest source tar ball( from http://pyyaml.org/download/pyyaml/) with libyaml, and run test suite, lot of tests fails due data malformation. It is caused by type cast from int to size_t in file _yaml.c function prototype(s) _pyx_f_5_yaml_input_handler.
As file is not present in this repo, I am not aware of way to propose patch/PR to fix it. And I was unsuccessful in building from repo( even on x86 running fedora20 due to missing _yaml.c ).
Please look in to it.
Link to fedora bz ticket: https://bugzilla.redhat.com/show_bug.cgi?id=1140189 (in attachment is patch with changes to _yaml.c)