Handle `u'' in ''`

src/runtime/str.cpp

@@ -1757,6 +1757,14 @@ Box* strSwapcase(BoxedString* self) {
 
 Box* strContains(BoxedString* self, Box* elt) {
     assert(self->cls == str_cls);
+
+    if (PyUnicode_Check(elt)) {
+        int r = PyUnicode_Contains(self, elt);
+        if (r < 0)
+            throwCAPIException();
+        return boxBool(r);
+    }
+
     if (elt->cls != str_cls)
         raiseExcHelper(TypeError, "'in <string>' requires string as left operand, not %s", getTypeName(elt));
 

test/tests/unicode_test.py

@@ -57,3 +57,11 @@ for i in xrange(100):
     # do some allocations:
     for j in xrange(100):
         [None] * j
+
+print u'' in ''
+print '' in u''
+print u'aoeu' in ''
+print u'\u0180' in 'hello world'
+print 'hello world' in u'\u0180'
+print u''.__contains__('')
+print ''.__contains__(u'')