Implemented Error trait for PyErr

src/err.rs

@@ -28,6 +28,8 @@ use std::ptr;
 use libc::c_char;
 use conversion::ToPyObject;
 use std::ffi::CString;
+use std::error::Error;
+use std::fmt;
 
 /**
 Defines a new exception type.
@@ -394,6 +396,18 @@ impl <'p> std::convert::From<PythonObjectDowncastError<'p>> for PyErr {
     }
 }
 
+impl Error for PyErr {
+    fn description(&self) -> &str {
+        "Error originating from the rust-cpython bindings."
+    }
+}
+
+impl fmt::Display for PyErr {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        write!(f, "PyErr: ptype {:?} pvalue {:?}", self.ptype, self.pvalue)
+    }
+}
+
 /// Construct PyObject from the result of a Python FFI call that returns a new reference (owned pointer).
 /// Returns `Err(PyErr)` if the pointer is `null`.
 /// Unsafe because the pointer might be invalid.