gnu: pybugz: Add fixlet patches.

* gnu/packages/python.scm (python2-pybugz)[source]: Add 'patches'
  field.
* gnu/packages/patches/pybugz-encode-error.patch,
  gnu/packages/patches/pybugz-stty.patch: New files.
* gnu-system.am (dist_patch_DATA): Add them.