Fix bugs in readinst(): * There was no error reported if the .read() method returns a non-string * If read() returned too much data, the buffer would be overflowed causing a   core dump * Used strncpy, not memcpy, which seems incorrect if there are embedded \0s. * The args and bytes objects were leaked
Fix bugs in readinst():
* There was no error reported if the .read() method returns a non-string
* If read() returned too much data, the buffer would be overflowed causing a
  core dump
* Used strncpy, not memcpy, which seems incorrect if there are embedded \0s.
* The args and bytes objects were leaked

sk-/python2.7-type-annotator,sk-/python2.7-type-annotator,sk-/python2.7-type-annotator