Adding cython v0.20.2 in third-party.

third_party/cython/src/Cython/Utility/CppSupport.cpp

Index: third_party/cython/src/Cython/Utility/CppSupport.cpp
diff --git a/third_party/cython/src/Cython/Utility/CppSupport.cpp b/third_party/cython/src/Cython/Utility/CppSupport.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..ab2f2b5b26d79bfe631c17258a88925d98f45499
--- /dev/null
+++ b/third_party/cython/src/Cython/Utility/CppSupport.cpp
@@ -0,0 +1,46 @@
+/////////////// CppExceptionConversion.proto ///////////////
+
+#ifndef __Pyx_CppExn2PyErr
+#include <new>
+#include <typeinfo>
+#include <stdexcept>
+#include <ios>
+
+static void __Pyx_CppExn2PyErr() {
+  // Catch a handful of different errors here and turn them into the
+  // equivalent Python errors.
+  try {
+    if (PyErr_Occurred())
+      ; // let the latest Python exn pass through and ignore the current one
+    else
+      throw;
+  } catch (const std::bad_alloc& exn) {
+    PyErr_SetString(PyExc_MemoryError, exn.what());
+  } catch (const std::bad_cast& exn) {
+    PyErr_SetString(PyExc_TypeError, exn.what());
+  } catch (const std::domain_error& exn) {
+    PyErr_SetString(PyExc_ValueError, exn.what());
+  } catch (const std::invalid_argument& exn) {
+    PyErr_SetString(PyExc_ValueError, exn.what());
+  } catch (const std::ios_base::failure& exn) {
+    // Unfortunately, in standard C++ we have no way of distinguishing EOF
+    // from other errors here; be careful with the exception mask
+    PyErr_SetString(PyExc_IOError, exn.what());
+  } catch (const std::out_of_range& exn) {
+    // Change out_of_range to IndexError
+    PyErr_SetString(PyExc_IndexError, exn.what());
+  } catch (const std::overflow_error& exn) {
+    PyErr_SetString(PyExc_OverflowError, exn.what());
+  } catch (const std::range_error& exn) {
+    PyErr_SetString(PyExc_ArithmeticError, exn.what());
+  } catch (const std::underflow_error& exn) {
+    PyErr_SetString(PyExc_ArithmeticError, exn.what());
+  } catch (const std::exception& exn) {
+    PyErr_SetString(PyExc_RuntimeError, exn.what());
+  }
+  catch (...)
+  {
+    PyErr_SetString(PyExc_RuntimeError, "Unknown exception");
+  }
+}
+#endif