fix(dns): parsing of /etc/resolv.conf by manually updating resolv-conf crate (#184)

* Show the error cause if initializing a DNS resolver fails

* Manually bump `resolv-conf` to `master` at rev `83c0f25`

This fixes the parsing of `/etc/resolv.conf` with `options trust-ad`
which is e.g. used in `systemd-resolved-v246`[1].

Refs #166

[1] systemd/systemd@a742f98

Author: Ma27

Cargo.lock

@@ -33,6 +33,7 @@ tokio = { version = "0.2", features = ["rt-core", "sync"] }
 trust-dns-resolver = "0.18.1"
 async-trait = "0.1.21"
 unicode-width = "0.1.8"
+resolv-conf = "0.6.3"
 
 [target.'cfg(target_os="windows")'.dependencies]
 netstat2 = "0.9.0"
@@ -51,3 +52,6 @@ regex = "1"
 [target.'cfg(target_os="windows")'.build-dependencies]
 http_req = "0.7.0"
 zip = "0.5.6"
+
+[patch.crates-io]
+resolv-conf = { git = 'https://github.com/tailhook/resolv-conf', rev = '83c0f25ebcb0615550488692c5213ca1ae4acd8f' }

Cargo.toml

@@ -238,7 +238,10 @@ pub fn get_input(
         let mut runtime = Runtime::new()?;
         let resolver = match runtime.block_on(dns::Resolver::new(runtime.handle().clone())) {
             Ok(resolver) => resolver,
-            Err(_) => failure::bail!("Could not initialize the DNS resolver. Are you offline?"),
+            Err(err) => failure::bail!(
+                "Could not initialize the DNS resolver. Are you offline?\n\nReason: {:?}",
+                err
+            ),
         };
         let dns_client = dns::Client::new(resolver, runtime)?;
         Some(dns_client)