- Do not apply HTTPs redirection for challenge used by the test.
- Set the `User-Agent` to avoid 403 answer from site24x7.com.
- Handle JSON parsing failure of the received body.
- Better handling of different error cases.
This fixes scenarios where `resolv.conf` generated by dhcpcd has a nameserver with `%interface` appended to its IPv6 address.
For example, a line like this must be properly handled:
nameserver fe80::7747:4aff:fe9a:8cb1%br0
This reverts commit f9876326c9.
This is to make sure the browser doesn't show a certificate warning (for a connection that will be dropped anyway) by breaking the SSL handshake early.