don't compile slow-path exception branches

Author: timfel

graalpython/com.oracle.graal.python/src/com/oracle/graal/python/builtins/modules/PythonCextBuiltins.java

@@ -843,8 +843,10 @@ Object doIt(VirtualFrame frame,
             try {
                 return fromNative(asPythonObjectNode.execute(checkResultNode.execute(name, lib.execute(fun, arguments))));
             } catch (UnsupportedTypeException | UnsupportedMessageException e) {
+                CompilerDirectives.transferToInterpreter();
                 throw raiseNode.raise(PythonBuiltinClassType.TypeError, "Calling native function %s failed: %m", name, e);
             } catch (ArityException e) {
+                CompilerDirectives.transferToInterpreter();
                 throw raiseNode.raise(PythonBuiltinClassType.TypeError, "Calling native function %s expected %d arguments but got %d.", name, e.getExpectedArity(), e.getActualArity());
             } finally {
                 // special case after calling a C function: transfer caught exception back to frame