There is an ongoing outage on the primary CPAN mirror. It is possible to work around the issue by using MetaCPAN as a mirror.

Change log for PerlIO::via::json

0.02   2017-02-05
  - adjusted t/020-write.t to workaround a bug in XML::XML2JSON
    (reported by various CPAN testers)
0.01   2009-02-01
  - Initial release