Fixes assertAllEqual() function in framework/test_util.py such that the function has the originally intended behavior without breaking PY3 compatibility.

PiperOrigin-RevId: 313906279
Change-Id: I267a8310e0bad813a7dbcf28f5e14b9f4cd66203

tensorflow/python/framework/test_util.py

@@ -2713,8 +2713,26 @@ class TensorFlowTestCase(googletest.TestCase):
         x, y = a, b
       msgs.append("not equal lhs = %r" % x)
       msgs.append("not equal rhs = %r" % y)
-      # With Python 3, we need to make sure the dtype matches between a and b.
-      b = b.astype(a.dtype)
+
+      # Handle mixed string types as a result of PY2to3 migration. That is, the
+      # mixing between bytes (b-prefix strings, PY2 default) and unicodes
+      # (u-prefix strings, PY3 default).
+      if six.PY3:
+        if (a.dtype.kind != b.dtype.kind and
+            {a.dtype.kind, b.dtype.kind}.issubset({"U", "S", "O"})):
+          a_list = []
+          b_list = []
+          # OK to flatten `a` and `b` because they are guaranteed to have the
+          # same shape.
+          for out_list, flat_arr in [(a_list, a.flat), (b_list, b.flat)]:
+            for item in flat_arr:
+              if isinstance(item, str):
+                out_list.append(item.encode("utf-8"))
+              else:
+                out_list.append(item)
+          a = np.array(a_list)
+          b = np.array(b_list)
+
       np.testing.assert_array_equal(a, b, err_msg="\n".join(msgs))
 
   @py_func_if_in_function