Change add reverse behaviour and delete hard coded "None" string.

Author: Franziska Geiger

graalpython/com.oracle.graal.python/src/com/oracle/graal/python/builtins/objects/object/ObjectBuiltins.java

@@ -300,7 +300,7 @@ String repr(VirtualFrame frame, Object self,
                         @Cached("create(__MODULE__)") GetFixedAttributeNode readModuleNode,
                         @Cached("create(__QUALNAME__)") GetFixedAttributeNode readQualNameNode) {
             if (self == PNone.NONE) {
-                return "None";
+                return "";
             }
             PythonAbstractClass type = getClass.execute(self);
             Object moduleName = readModuleNode.executeObject(frame, type);

graalpython/com.oracle.graal.python/src/com/oracle/graal/python/builtins/objects/str/StringBuiltins.java

@@ -447,7 +447,12 @@ protected boolean concatGuard(CharSequence left, CharSequence right) {
 
     @Builtin(name = __RADD__, minNumOfPositionalArgs = 2)
     @GenerateNodeFactory
-    public abstract static class RAddNode extends AddNode {
+    public abstract static class RAddNode {
+        @Specialization
+        Object doAll(VirtualFrame frame, Object left, Object right,
+                     @Cached("create()") AddNode addNode) {
+            return addNode.execute(frame, right, left);
+        }
     }
 
     // str.startswith(prefix[, start[, end]])