It wasn't Pope Francis. It was the work of the Italian bishops.  

Socci, who is a native Italian speaker, also called attention to the matter on his Facebook page. His article in Libero is entitled,”‘That Devil Jesus’. Words of Bergoglio.” This article itself is not available online but the author just posted a follow-up article that was published in Libero today, Apr. 6:

What exactly did Francis say? The official summary (with copious verbatim quotes) of his April 4, 2017 sermon at the Casa Santa Marta appears in the Vatican’s own newspaper, Osservatore Romano, vol. CLVII, n. 79 (Apr. 5, 2017). It is also found on the Vatican web site:

An official and complete English translation of the text has not been released, but Vatican Radio has published an English summary, which, however, omits the most explosive portion of the homily and does not do justice to the original Italian text found on the Vatican web site:

In this homily, Francis continually emphasizes how Christ “became sin” for us (mentioning this phrase as many as seven times), and he exaggerates it beyond its orthodox meaning. It appears he enjoys doing so by the sheer repetition and undue emphasis of this phrase. This isn’t new for him — he has done it before, as for example in his homily of June 15, 2013, in which he claimed that Christ “became the sinner” for us, and in his sermon of March 15, 2016, in which he asserted that our Lord “became sin” and “a serpent”.
This time, however, Francis managed to outdo himself, virtually eclipsing his prior utterances. Speaking of the Cross, the Crucifix, as the badge of the Christian, Francis called it “the memory of him who has made himself sin, who has made himself the devil, the serpent, for us; he has humbled himself to the point of complete annihilation.” The exact Italian reads: “come memoria di colui che si è fatto peccato, che si è fatto diavolo, serpente, per noi; si è abbassato fino ad annientarsi totalmente“. These words are printed on the Vatican web site as linked above.
Under the cloak of admiring God’s humility, Francis claims that Jesus Christ Himself is the devil! Once again, Bergoglio shows himself firmly ensconced in the camp of his real masters, the apostate Jєωs, for this was the same insult the unbelieving Pharisees hurled at our Lord, as He lamented: “they have called the goodman of the house Beelzebub” (Mt 10:25; cf. Mt 12:24-30; Jn 8:52).
A more staggering blasphemy than to say that God is Satan cannot be imagined!
And yet there it is, right there on the various web sites of the Vatican.

The Pope gives directions to those Italian Bishops.