When St Francis renounced his earthly possessions, it is reputed that he dressed himself in "(a) coarse woollen tunic, the dress then worn by the poorest Umbrian peasants, (tied) around himself with a knotted rope".

I doubt that the current members of the Franciscan order do the same if only because it's unlikely that coarse woollen tunics are easily available. Nonetheless, the friars that I saw at the basilica did wear tunics (I'm not sure that you would call these cassocks) of a similar style, still with ropes around the middle, just as this one who is entering the lower basilica is wearing.

You probably won't be able to see it from the resized image for this gallery, but I noticed that they also tend to wear sandals rather than shoes. I'm not sure how that would go in the winter, but there is a reason that I'm not a friar in a religious order. Actually, many reasons of which that would be one, and not one of the most important ones.

I notice the term "Jubilee Year" on the left-hand side of the door. I was indeed wondering "WHAT Jubilee?", since I wasn't aware of the anniversary of anything. As it turns out there is an additional meaning for the word, one that I had not previously known about:
"A period of remission from the penal consequences of sin, granted by the Roman Catholic Church under certain conditions for a year, usually at intervals of twenty-five years."

Apparently Pope Francis declared a special Jubilee "Year of Mercy" in November 2015 to 2016. That's what the banner is referring to.