System crash when using pyjulia.

Hello,

Background:

I am using Julia v 0.6.2 and Python 3.6.3 (installed using Continuum's Anaconda) on Ubuntu 16.04 LTS.
I have to run julia command line application with the following command (https://github.com/JuliaPy/PyPlot.jl/issues/151):

> LD_PRELOAD=/home/phn/bin/anaconda3/envs/py36/lib/libz.so ~/bin/julia-d386e40c17/bin/julia

pyjulia was installed indirectly when I installed the "diffeqpy" package. The problem showed up when trying to use diffeqpy and I raised an issue there. The author of diffeqpy found that the problem was occurring when running pyjulia and asked me to raise an issue here (https://github.com/JuliaDiffEq/diffeqpy/issues/27).

----

Issue:

When I run

```python
j = julia.Julia()
```

I get

In [3]: j = julia.Julia()
PyError (ccall(@pysym(:PyObject_Call), PyPtr, (PyPtr, PyPtr, PyPtr), o, arg, C_NULL)) PyError (ccall(@pysym(:PyObject_Call), PyPtr, (PyPtr, PyPtr, PyPtr), o, arg, C_NULL)) PyError (ccall(@pysym(:PyObject_Call), PyPtr, (PyPtr, PyPtr, PyPtr), o, arg, C_NULL)) PyError (ccall(@pysym(:PyObject_Call), PyPtr, (PyPtr, PyPtr, PyPtr), o, arg, C_NULL))

When I then run

```python
j.sind(90)
```

the system crashes with the following message

In [4]: j.sind(90)
fatal: error thrown and no exception handler available.
PyCall.PyError(msg="ccall(@pysym(PyString_AsStringAndSize), Cint, (PyPtr, Ptr{Ptr{UInt8}}, Ptr{Int}), po, _ps_ptr, _ps_len)", T=PyCall.PyObject(o=0x000055f323468f40), val=PyCall.PyObject(o=0x00007f2a77ab6f68), traceback=PyCall.PyObject(o=0x0000000000000000))
rec_backtrace at /buildworker/worker/package_linux64/build/src/stackwalk.c:84
record_backtrace at /buildworker/worker/package_linux64/build/src/task.c:245
jl_throw at /buildworker/worker/package_linux64/build/src/task.c:564
pyerr_check at /home/phn/.julia/v0.6/PyCall/src/exception.jl:58 [inlined]
pyerr_check at /home/phn/.julia/v0.6/PyCall/src/exception.jl:62 [inlined]
macro expansion at /home/phn/.julia/v0.6/PyCall/src/exception.jl:82 [inlined]
convert at /home/phn/.julia/v0.6/PyCall/src/conversions.jl:111
pystring at /home/phn/.julia/v0.6/PyCall/src/PyCall.jl:224
show at /home/phn/.julia/v0.6/PyCall/src/PyCall.jl:229
show_delim_array at ./show.jl:381
show at ./show.jl:397
unknown function (ip: 0x7f2a5ac9d1b6)
jl_call_fptr_internal at /buildworker/worker/package_linux64/build/src/julia_internal.h:339 [inlined]
jl_call_method_internal at /buildworker/worker/package_linux64/build/src/julia_internal.h:358 [inlined]
jl_apply_generic at /buildworker/worker/package_linux64/build/src/gf.c:1926
show_default at ./show.jl:140
unknown function (ip: 0x7f2a5ac9cc66)
jl_call_fptr_internal at /buildworker/worker/package_linux64/build/src/julia_internal.h:339 [inlined]
jl_call_method_internal at /buildworker/worker/package_linux64/build/src/julia_internal.h:358 [inlined]
jl_apply_generic at /buildworker/worker/package_linux64/build/src/gf.c:1926
jl_apply at /buildworker/worker/package_linux64/build/src/julia.h:1424 [inlined]
jl_invoke at /buildworker/worker/package_linux64/build/src/gf.c:51
print at ./strings/io.jl:29
unknown function (ip: 0x7f2a5ac9c436)
jl_call_fptr_internal at /buildworker/worker/package_linux64/build/src/julia_internal.h:339 [inlined]
jl_call_method_internal at /buildworker/worker/package_linux64/build/src/julia_internal.h:358 [inlined]
jl_apply_generic at /buildworker/worker/package_linux64/build/src/gf.c:1926
#print_to_string#229 at ./strings/io.jl:102
pyraise at /home/phn/.julia/v0.6/PyCall/src/exception.jl:127
unknown function (ip: 0x7f2a5ac9bfe2)
jl_call_fptr_internal at /buildworker/worker/package_linux64/build/src/julia_internal.h:339 [inlined]
jl_call_method_internal at /buildworker/worker/package_linux64/build/src/julia_internal.h:358 [inlined]
jl_apply_generic at /buildworker/worker/package_linux64/build/src/gf.c:1926
_pyjlwrap_call at /home/phn/.julia/v0.6/PyCall/src/callback.jl:56
unknown function (ip: 0x7f2a5ac906f5)
jl_call_fptr_internal at /buildworker/worker/package_linux64/build/src/julia_internal.h:339 [inlined]
jl_call_method_internal at /buildworker/worker/package_linux64/build/src/julia_internal.h:358 [inlined]
jl_apply_generic at /buildworker/worker/package_linux64/build/src/gf.c:1926
pyjlwrap_call at /home/phn/.julia/v0.6/PyCall/src/callback.jl:63
unknown function (ip: 0x7f2a5ac66a9f)
_PyObject_FastCallDict at /home/phn/bin/anaconda3/envs/py36/bin/python (unknown line)
unknown function (ip: 0x55f3230e800d)
_PyEval_EvalFrameDefault at /home/phn/bin/anaconda3/envs/py36/bin/python (unknown line)
PyEval_EvalCodeEx at /home/phn/bin/anaconda3/envs/py36/bin/python (unknown line)
PyEval_EvalCode at /home/phn/bin/anaconda3/envs/py36/bin/python (unknown line)
unknown function (ip: 0x55f323106f2d)
_PyCFunction_FastCallDict at /home/phn/bin/anaconda3/envs/py36/bin/python (unknown line)
unknown function (ip: 0x55f3230e7ebb)
_PyEval_EvalFrameDefault at /home/phn/bin/anaconda3/envs/py36/bin/python (unknown line)
unknown function (ip: 0x55f3230e0f23)
unknown function (ip: 0x55f3230e1dc0)
unknown function (ip: 0x55f3230e7f94)
_PyEval_EvalFrameDefault at /home/phn/bin/anaconda3/envs/py36/bin/python (unknown line)
unknown function (ip: 0x55f3230e0f23)
unknown function (ip: 0x55f3230e1dc0)
unknown function (ip: 0x55f3230e7f94)
_PyEval_EvalFrameDefault at /home/phn/bin/anaconda3/envs/py36/bin/python (unknown line)
unknown function (ip: 0x55f3230e128d)
unknown function (ip: 0x55f3230e1dc0)
unknown function (ip: 0x55f3230e7f94)
_PyEval_EvalFrameDefault at /home/phn/bin/anaconda3/envs/py36/bin/python (unknown line)
unknown function (ip: 0x55f3230e0f23)
unknown function (ip: 0x55f3230e1dc0)
unknown function (ip: 0x55f3230e7f94)
_PyEval_EvalFrameDefault at /home/phn/bin/anaconda3/envs/py36/bin/python (unknown line)
unknown function (ip: 0x55f3230e0f23)
unknown function (ip: 0x55f3230e1dc0)
unknown function (ip: 0x55f3230e7f94)
_PyEval_EvalFrameDefault at /home/phn/bin/anaconda3/envs/py36/bin/python (unknown line)
unknown function (ip: 0x55f3230e1b8a)
unknown function (ip: 0x55f3230e7f94)
_PyEval_EvalFrameDefault at /home/phn/bin/anaconda3/envs/py36/bin/python (unknown line)
unknown function (ip: 0x55f3230e0f23)
_PyFunction_FastCallDict at /home/phn/bin/anaconda3/envs/py36/bin/python (unknown line)
_PyObject_FastCallDict at /home/phn/bin/anaconda3/envs/py36/bin/python (unknown line)
_PyObject_Call_Prepend at /home/phn/bin/anaconda3/envs/py36/bin/python (unknown line)
PyObject_Call at /home/phn/bin/anaconda3/envs/py36/bin/python (unknown line)
_PyEval_EvalFrameDefault at /home/phn/bin/anaconda3/envs/py36/bin/python (unknown line)
unknown function (ip: 0x55f3230e0f23)
unknown function (ip: 0x55f3230e1dc0)
unknown function (ip: 0x55f3230e7f94)
_PyEval_EvalFrameDefault at /home/phn/bin/anaconda3/envs/py36/bin/python (unknown line)
PyEval_EvalCodeEx at /home/phn/bin/anaconda3/envs/py36/bin/python (unknown line)
PyEval_EvalCode at /home/phn/bin/anaconda3/envs/py36/bin/python (unknown line)
unknown function (ip: 0x55f32315dce3)
PyRun_FileExFlags at /home/phn/bin/anaconda3/envs/py36/bin/python (unknown line)
PyRun_SimpleFileExFlags at /home/phn/bin/anaconda3/envs/py36/bin/python (unknown line)
Py_Main at /home/phn/bin/anaconda3/envs/py36/bin/python (unknown line)
main at /home/phn/bin/anaconda3/envs/py36/bin/python (unknown line)
__libc_start_main at /build/glibc-Cl5G7W/glibc-2.23/csu/../csu/libc-start.c:291
unknown function (ip: 0x55f3231100d9)

----

Hope this helps you identify the problem. Let me know if you need more information.

Thanks.

Regards,
Prasanth