FIX: account for change in how exception information is stored

CPython change how the exception information is stored internally in
3.7a3.

This simply adds fences based on python version around how to access
the objects.

Xref:

https://github.com/python/cpython/commit/ae3087c6382011c47db82fea4d05f8bbf514265d
https://bugs.python.org/issue25612
https://github.com/python/cpython/pull/1773

Cython/Utility/Exceptions.c

@@ -359,12 +359,21 @@ static int __Pyx_GetException(PyObject **type, PyObject **value, PyObject **tb)
     *value = local_value;
     *tb = local_tb;
 #if CYTHON_FAST_THREAD_STATE
+    #if PY_MAJOR_VERSION >= 3 && PY_MINOR_VERSION >= 7
+    tmp_type = tstate->exc_state.exc_type;
+    tmp_value = tstate->exc_state.exc_value;
+    tmp_tb = tstate->exc_state.exc_traceback;
+    tstate->exc_state.exc_type = local_type;
+    tstate->exc_state.exc_value = local_value;
+    tstate->exc_state.exc_traceback = local_tb;
+    #else
     tmp_type = tstate->exc_type;
     tmp_value = tstate->exc_value;
     tmp_tb = tstate->exc_traceback;
     tstate->exc_type = local_type;
     tstate->exc_value = local_value;
     tstate->exc_traceback = local_tb;
+    #endif
     // Make sure tstate is in a consistent state when we XDECREF
     // these objects (DECREF may run arbitrary code).
     Py_XDECREF(tmp_type);
@@ -394,9 +403,15 @@ static CYTHON_INLINE void __Pyx_ReraiseException(void) {
     PyObject *type = NULL, *value = NULL, *tb = NULL;
 #if CYTHON_FAST_THREAD_STATE
     PyThreadState *tstate = PyThreadState_GET();
+    #if PY_MAJOR_VERSION >= 3 && PY_MINOR_VERSION >= 7
+    type = tstate->exc_state.exc_type;
+    value = tstate->exc_state.exc_value;
+    tb = tstate->exc_state.exc_traceback;
+    #else
     type = tstate->exc_type;
     value = tstate->exc_value;
     tb = tstate->exc_traceback;
+    #endif
 #else
     PyErr_GetExcInfo(&type, &value, &tb);
 #endif
@@ -440,9 +455,15 @@ static CYTHON_INLINE void __Pyx__ExceptionReset(PyThreadState *tstate, PyObject
 
 #if CYTHON_FAST_THREAD_STATE
 static CYTHON_INLINE void __Pyx__ExceptionSave(PyThreadState *tstate, PyObject **type, PyObject **value, PyObject **tb) {
+    #if PY_MAJOR_VERSION >= 3 && PY_MINOR_VERSION >= 7
+    *type = tstate->exc_state.exc_type;
+    *value = tstate->exc_state.exc_value;
+    *tb = tstate->exc_state.exc_traceback;
+    #else
     *type = tstate->exc_type;
     *value = tstate->exc_value;
     *tb = tstate->exc_traceback;
+    #endif
     Py_XINCREF(*type);
     Py_XINCREF(*value);
     Py_XINCREF(*tb);
@@ -450,12 +471,22 @@ static CYTHON_INLINE void __Pyx__ExceptionSave(PyThreadState *tstate, PyObject *
 
 static CYTHON_INLINE void __Pyx__ExceptionReset(PyThreadState *tstate, PyObject *type, PyObject *value, PyObject *tb) {
     PyObject *tmp_type, *tmp_value, *tmp_tb;
+
+    #if PY_MAJOR_VERSION >= 3 && PY_MINOR_VERSION >= 7
+    tmp_type = tstate->exc_state.exc_type;
+    tmp_value = tstate->exc_state.exc_value;
+    tmp_tb = tstate->exc_state.exc_traceback;
+    tstate->exc_state.exc_type = type;
+    tstate->exc_state.exc_value = value;
+    tstate->exc_state.exc_traceback = tb;
+    #else
     tmp_type = tstate->exc_type;
     tmp_value = tstate->exc_value;
     tmp_tb = tstate->exc_traceback;
     tstate->exc_type = type;
     tstate->exc_value = value;
     tstate->exc_traceback = tb;
+    #endif
     Py_XDECREF(tmp_type);
     Py_XDECREF(tmp_value);
     Py_XDECREF(tmp_tb);
@@ -478,6 +509,16 @@ static CYTHON_INLINE void __Pyx_ExceptionSwap(PyObject **type, PyObject **value,
 #if CYTHON_FAST_THREAD_STATE
 static CYTHON_INLINE void __Pyx__ExceptionSwap(PyThreadState *tstate, PyObject **type, PyObject **value, PyObject **tb) {
     PyObject *tmp_type, *tmp_value, *tmp_tb;
+
+    #if PY_MAJOR_VERSION >= 3 && PY_MINOR_VERSION >= 7
+    tmp_type = tstate->exc_state.exc_type;
+    tmp_value = tstate->exc_state.exc_value;
+    tmp_tb = tstate->exc_state.exc_traceback;
+
+    tstate->exc_state.exc_type = *type;
+    tstate->exc_state.exc_value = *value;
+    tstate->exc_state.exc_traceback = *tb;
+    #else
     tmp_type = tstate->exc_type;
     tmp_value = tstate->exc_value;
     tmp_tb = tstate->exc_traceback;
@@ -486,6 +527,7 @@ static CYTHON_INLINE void __Pyx__ExceptionSwap(PyThreadState *tstate, PyObject *
     tstate->exc_value = *value;
     tstate->exc_traceback = *tb;
 
+    #endif
     *type = tmp_type;
     *value = tmp_value;
     *tb = tmp_tb;