It seems you're translating the encoded letter and reversing the other letters of the word.
That'll only work in words of less than 4 letters.

Only switch the second and the last chars, nothing else.

Test.assert_equals(decipher_this("65 119esi 111dl 111lw 108dvei 105n 97n 111ka"), "A wise old owl lived in an oak")

Isnt this a error in the python challenge? The decipher of this will be 'A wise old owl !!lievd!!! in an oak', which is the error i get.