This seems to have been fixed with 8452ca15f41061c8a6297d7956df22ab476d4df4. I checked out your example locally and renamed pickle.py to another name to avoid module collision. Ran the below commands to pickle using Python 2 and to unpickle from master before and after the relevant commit. The fix is present in 3.7 and 3.6.

➜  bpo36499 python2 pickledatetime.py

# with 8452ca15f41061c8a6297d7956df22ab476d4df4
➜  bpo36499 ../cpython/python.exe unpickledatetime.py
Pickle:  {'timenode': datetime.datetime(2019, 4, 2, 15, 13, 2, 675110)}

# with 8452ca15f41061c8a6297d7956df22ab476d4df4~1
➜  bpo36499 ../cpython/python.exe unpickledatetime.py
Traceback (most recent call last):
  File "unpickledatetime.py", line 22, in <module>
    main()
  File "unpickledatetime.py", line 18, in main
    pkl = unpickler.load()
  File "/Users/karthikeyansingaravelan/stuff/python/cpython/Lib/pickle.py", line 1081, in load
    dispatch[key[0]](self)
  File "/Users/karthikeyansingaravelan/stuff/python/cpython/Lib/pickle.py", line 1429, in load_reduce
    stack[-1] = func(*args)
TypeError: an integer is required (got type str)

# pickledatetime.py

import io
import pickle
from datetime import datetime


def main():
    """
    Uses python 2.7 to create a pickle file with a datetime object inside a dictionary.
    """
    data = {}
    data['timenode'] = datetime.now()
    with io.open('written_by_py27.pickle', 'wb') as handle:
        pickle.dump(data, handle, protocol=pickle.HIGHEST_PROTOCOL)

if __name__ == "__main__":
    main()

# unpickledatetime.py

import io
import pickle


def main():
    """
    Attempts to unpickle a dictionary with a datatype object inside
    """
    with io.open('written_by_py27.pickle', 'rb') as handle:
        unpickler = pickle._Unpickler(handle)
        unpickler.encoding = 'latin1'
        pkl = unpickler.load()
        print("Pickle: ", pkl)

if __name__ == "__main__":
    main()