When the popup appears, move the mouse over it and simply select (mark) the text of the bubble, then Copy with the keyboard arrow ( CTRL + C on Windows or Command + C on Mac), still having the mouse pointer over the bubble.
Not sure how on Mac, but on Windows it works for me, except that you need to constantly hold the mouse pointer over the bubble, otherwise it will go away (which sometimes makes me copy everything except the last character from this message).
source share