Fix for bug [ 561796 ] string.find causes lazy error

Include/unicodeobject.h

@@ -983,7 +983,8 @@ extern DL_IMPORT(int) PyUnicode_Tailmatch(
     );
 
 /* Return the first position of substr in str[start:end] using the
-   given search direction or -1 if not found. */
+   given search direction or -1 if not found. -2 is returned in case
+   an error occurred and an exception is set. */
 
 extern DL_IMPORT(int) PyUnicode_Find(
     PyObject *str,		/* String */ 

Objects/unicodeobject.c

@@ -2887,11 +2887,11 @@ int PyUnicode_Find(PyObject *str,
     
     str = PyUnicode_FromObject(str);
     if (str == NULL)
-	return -1;
+	return -2;
     substr = PyUnicode_FromObject(substr);
     if (substr == NULL) {
 	Py_DECREF(substr);
-	return -1;
+	return -2;
     }
     
     result = findstring((PyUnicodeObject *)str,