Short answer: 7" width rims with +35mm offset fit my 500e without spacers. MY 205s barely clear, but not all 205s are the same width!!!
Details: Please note that every 17" wheel/tire set I found is heavier than 16", which is heavier than 15". 17s look great, & increase road feel & response, while sacrificing acceleration, braking, range-per-charge, & un-smooth road handling.
That said, I have 7" rims all-around (15"), with +35mm offset, in 205s, & they fit nicely. Keep in mind that 205s don't all have the same overall width, or even tread width. Also note that the closest clearance limit is on the rear inner sidewall, where there's a bracket that comes close to my 205s. When I noticed mine, it looked like it was probably weak enough to bend a bit out of the way if necessary (like if my next 205s are wider, or if I try for 215s).