sslutil: move code examining _canloaddefaultcerts out of _defaultcacerts Before, the return of _defaultcacerts() was 1 of 3 types. This was difficult to read. Make it return a path or None. We had to update hghave.py in the same patch because it was also looking at this internal function. I wasted dozens of minutes trying to figure out why tests were failing until I found the code in hghave.py...