Passing PyObject through include/eval turns it into PyNULL (which causes segfaults)

[tkf]

julia> using PyCall

julia> obj = pyimport("sys")  # get some PyObject
PyObject <module 'sys' (built-in)>

julia> py"""
       ns = {}
       def set(name):
           ns[name] = $include_string($Main, name)
       """

julia> py"set"("obj")

julia> obj
PyObject NULL

julia> py"lambda x: x"(obj)

signal (11): Segmentation fault

There are two problems: (1) py"set"("obj") turns obj to PyNULL (ref count issue?) and (2) passing PyNULL to Python function is not guarded enough.

Note that py"set" is modeling what we do in PyJulia all the time so it's not a contrived example.