Mandeep S.S. Gill reports:

have found what appears to be an error inside of: `afw/python/lsst/afw/display/ds9.py`, in current line 54: ``` self.exception = type(e)("%s (is display_d9 setup?)" % e) ``` which you can just see by sight needs correcting to: `display_ds9` in the parens.

(ie, there is a missing "s").