call_method*() crashes when the method does not exist

[Vlad-Shcherbina]

extern crate pyo3;

use pyo3::{Python, ObjectProtocol};

fn main() {
    let gil = Python::acquire_gil();
    let py = gil.python();
    let a = py.eval("42", None, None).unwrap();
    a.call_method0("__str__").unwrap();  // ok
    a.call_method0("nonexistent_method").unwrap();  // crashes
}

Ideally should produce AttributeError or something.

---

This happens because in

pyo3/src/objectprotocol.rs

Lines 329 to 340 in 30baa99

	fn call_method0(&self, name: &str) -> PyResult<&PyObjectRef>
	{
	name.with_borrowed_ptr(self.py(), |name| unsafe {
	let ptr = ffi::PyObject_GetAttr(self.as_ptr(), name);
	let args = PyTuple::empty(self.py()).into_ptr();
	let result = self.py().from_owned_ptr_or_err(
	ffi::PyObject_Call(ptr, args, std::ptr::null_mut()));
	ffi::Py_DECREF(ptr);
	self.py().xdecref(args);
	result
	})
	}

and several similar places, ptr could be NULL.

[fafhrd91]

we should return PyErr if ptr is null,

https://github.com/PyO3/pyo3/blob/master/src/err.rs#L239

[fafhrd91]

fixed in master