Oh, sorry, I did not notice test_yaml_linkage. And in any case this test was broken (should be rv[1][0] instead of rv[1]).

I don't like to revert these changes, and the reversion can break a code written for 3.4 which pickles recursive OrderedDicts. I suggest following solution. PyYAML calls __reduce_ex_(2) or __reduce__(). Therefore we can return to old behavior with protocol < 3 and left current behavior with protocol >= 3. Recursive OrderedDicts will be pickleable with default protocol and with highest protocol, and PyYAML will be happy.

Does this patch look good to your?