dmsgcurl exits without error on failure to connect or http error

[0pcom]

When using dmsgcurl via script to check a visor's /health over dmsg in order to determine if one should create a transport to that visor or if that visor can be reached over dmsg, it's critical that the exit status of dmsgcurl should more reflect the behavior of curl in the same instance.

$ skywire dmsg curl -l debug dmsg://$(skywire cli config gen-keys | head -n1):80/health ; echo "Exit status $?"
[2024-04-06T10:23:56.860428249-05:00] DEBUG disc.NewHTTP [dmsgcurl]: Created HTTP client. addr="http://dmsgd.skywire.skycoin.com"
[2024-04-06T10:23:56.860467083-05:00] DEBUG [dmsgcurl]: Connecting to dmsg network... dmsg_disc="http://dmsgd.skywire.skycoin.com" public_key="020dd574b5fbeac3f2865ea3cf7080eaf48671e447df5182f1d2b488f2c7ceb957"
[2024-04-06T10:23:56.860529004-05:00] DEBUG [dmsg_client]: Discovering dmsg servers...
[2024-04-06T10:23:57.376771725-05:00] DEBUG [dmsg_client]: Dialing session... remote_pk=03717576ada5b1744e395c66c2bb11cea73b0e23d0dcd54422139b1a7f12e962c4
[2024-04-06T10:23:58.200998802-05:00] DEBUG [dmsg_client]: Serving session. remote_pk=03717576ada5b1744e395c66c2bb11cea73b0e23d0dcd54422139b1a7f12e962c4
[2024-04-06T10:23:58.201058547-05:00] DEBUG [dmsgcurl]: Dmsg network ready.
[2024-04-06T10:23:58.696210807-05:00] ERROR [dmsgcurl]: error="failed to connect to HTTP server: Get "dmsg://02153a3aa4424a745b54fa550b083e91c627abe07299619f24ef6611e26dda45fa:80/health": dmsg error 100 - entry is not found in discovery"
[2024-04-06T10:23:58.696453651-05:00] DEBUG [dmsg_client]: Stopped accepting streams. error="session shutdown" session=03717576ada5b1744e395c66c2bb11cea73b0e23d0dcd54422139b1a7f12e962c4
[2024-04-06T10:23:58.696461474-05:00] DEBUG [dmsg_client]: Stopped serving client!
[2024-04-06T10:23:58.696533555-05:00] DEBUG [dmsg_client]: Session closed. error=<nil>
[2024-04-06T10:23:58.696568164-05:00] DEBUG [dmsg_client]: All sessions closed.
[2024-04-06T10:23:58.934299388-05:00] DEBUG [dmsg_client]: Deleting entry. entry=	version: 0.0.1
	sequence: 0
	registered at: 1712417037945352160
	static public key: 020dd574b5fbeac3f2865ea3cf7080eaf48671e447df5182f1d2b488f2c7ceb957
	signature: e91b16e760291f5b7db9e973ad35ec270d3fd7a5a742daf51a152280b190774f1bde5b54ea76816a4c4e764e1786f99622f91ab0ab6aba8466b37f2f757294c700
	entry is registered as client. Related info: 
		delegated servers: 
			03717576ada5b1744e395c66c2bb11cea73b0e23d0dcd54422139b1a7f12e962c4


[2024-04-06T10:23:59.178884521-05:00] DEBUG [dmsg_client]: Entry Deleted successfully.
[2024-04-06T10:23:59.178932201-05:00] DEBUG [dmsgcurl]: Disconnected from dmsg network. error=<nil>

Exit status 0

For comparison, the behavior of curl when a website is not found

$ curl -L http://nonexistantwebsite.com/ ; echo "Exit status: $?"
curl: (6) Could not resolve host: nonexistantwebsite.com
Exit status: 6

[0pcom]

I've come up with a workaround using dmsgweb which is much faster than dmsgcurl when it comes to bulk downloads

$ curl -Lx socks5h://127.0.0.1:4445 http://$(skywire cli visor pk).dmsg/health 
{"build_info":{"version":"v1.3.20","commit":"8e782b1","date":"2024-03-23T01:29:00Z"},"started_at":"2024-04-06T12:41:54.253875421-05:00"}